Fix cmsg(3) bugs for musl and OSX

This PR fixes bugs in the cmsg(3) family of functions for Linux/musl and OSX, introduced by PR #1098 and PR #1212 .  It also adds an integration test which hopefully will validate these functions on every platform.

Since these are defined in C as macros, they must be reimplemented in
libc as Rust functions.  They're hard to get exactly right, and they
vary from platform to platform.  The test builds custom C code that uses
the real macros, and compares its output to the Rust versions' output
for various inputs.

Skip the CMSG_NXTHDR test on sparc64 linux because it hits a Bus Error.

Issue #1239

Skip the entire cmsg test program on s390x because it dumps core
seemingly before the kernel finishes booting.

Issue #1240

This is an error from PR #1098.  The wrong definitions coincidentally
work on Linux/glibc, but fail on Linux/musl.

This was an oversight from PR #1212.  It's been revealed by the new cmsg
test.

Update runtest-android

Keep the implementation in sync with packed_simd and stdsimd.

RFC 2235 - Implement PartialEq,Eq,Hash,Debug for all types

First pass at implementing [RFC2235](https://github.com/rust-lang/rfcs/blob/master/text/2235-libc-struct-traits.md). I just started with `PartialEq`/`Eq` and tested locally on my x64 Linux system. Definitely going to run into other types for other platforms that need this treatment, but thought I'd start small.

Open question is whether this should also rely on the `align` feature, which should improve which types can be auto-derived versus manually implemented (as it removed a lot of odd-sized padding arrays). My first pass here doesn't do that, but I might test it out to see if it does simplify quite a few structs. I think it might also be nice to have as it makes it easier for contributors to add new structs.

Part of rust-lang/rust#57715

Added inotify bindings.

Hi, I'd like to add inotify bindings. This is a first throw at it. Can you guide me through the process of merging it ?

Add powerpc64-unknown-freebsd

FreeBSD review: https://reviews.freebsd.org/D18367

This is used for running style checks on the libc codebase but shouldn't
be committed, so adding it to the .gitignore file.

This was not compile-tested on all platforms, but instead all `pub enum`
types had a `Debug` impl derived for them.

Add FreeBSD armv6 and armv7 targets

This was an artifact from when a git dependency on ctest was used. This
is no longer the case, so removing it to simplify future PRs.

Bump to 0.2.48

Bumps libc version to 0.2.48. This release contains the breaking changes performed in #1222 .

fix stack_t on FreeBSD

FreeBSD 10.x is EOL, in FreeBSD 11 and later, ss_sp is actually a void* [1]
dragonflybsd still uses c_char [2]

[1] https://svnweb.freebsd.org/base/releng/11.2/sys/sys/signal.h?revision=334459&view=markup#l438
[2] https://github.com/DragonFlyBSD/DragonFlyBSD/blob/master/sys/sys/signal.h#L339

should be committed with https://github.com/rust-lang/rust/pull/57810

dragonflybsd still uses c_char [2]

[1] https://svnweb.freebsd.org/base/releng/11.2/sys/sys/signal.h?revision=334459&view=markup#l438
[2] https://github.com/DragonFlyBSD/DragonFlyBSD/blob/master/sys/sys/signal.h#L339

Re-enable android build jobs

This performs a `yes | ./sdk/tools/bin/sdkmanager --licenses` - the sole purpose of the `--licenses` flag is to allow the user to accept all licenses a priori, so that all other commands don't show any licenses.

For some reason, after all licenses have been accepted, the install step says that some licenses are still not accepted... so we need to accept those too... Why? I have no idea, and accepting licenses while installing still appears to make things hang a little, but it only does so for one non-accepted license, instead of for 5-6 like before, so now things do work.

Closes #1170 .

Fix CMSG_DATA(3) and friends on BSD

PR #1098 added the CMSG_DATA(3) family of functions into libc.  Because
they're defined as macros in C, they had to be rewritten as Rust
functions for libc.  Also, they can't be tested in CI for the same
reason.  But that PR erroneously used the same definitions in BSD as in
Linux.

This commit corrects the definitions for OSX, FreeBSD, DragonflyBSD,
OpenBSD, and NetBSD.  I renamed a few variables and collapsed a few
macros in order to combine the definitions where possible.

Fixes #1210

PR #1098 added the CMSG_DATA(3) family of functions into libc.  Because
they're defined as macros in C, they had to be rewritten as Rust
functions for libc.  Also, they can't be tested in CI for the same
reason.  But that PR erroneously used the same definitions in BSD as in
Linux.

This commit corrects the definitions for OSX, FreeBSD, DragonflyBSD,
OpenBSD, and NetBSD.  I renamed a few variables and collapsed a few
macros in order to combine the definitions where possible.

Fixes #1210

Fix linking aio_read(3) and friends on NetBSD

The aio functions require librt on NetBSD.

Remove fexecve from netbsdlike as it's not implemented

Sometimes it causes confusion in downstream users of libc, for example it caused nix-rust/nix to fail to compile on OpenBSD 6.4 (see https://github.com/nix-rust/nix/pull/1000).

OpenBSD doesn't implement fexecve. The only reference of it that I can
find in the OpenBSD source is in the man pages of signal(3) and
sigaction(2) (where it's mentioned that it is not implemented).

OpenBSD official source code link:
https://cvsweb.openbsd.org/src/lib/libc/sys/sigaction.2?rev=1.75&content-type=text/x-cvsweb-markup

OpenBSD Github mirror:
https://github.com/openbsd/src/blob/master/lib/libc/sys/sigaction.2#L619

On NetBSD's unistd.h I see that it is under an ifdef. Calling it returns
78 / ENOSYS / Function not implemented.

NetBSD office source code link:
http://cvsweb.netbsd.org/bsdweb.cgi/src/include/unistd.h?rev=1.151&content-type=text/x-cvsweb-markup&only_with_tag=MAIN

NetBSD Github mirror:
https://github.com/NetBSD/src/blob/trunk/include/unistd.h#L319

Tests on OpenBSD 6.4 after the change:
```bash
user@openbsd64 ~/RUST/libc $ cargo build
   Compiling libc v0.2.46 (/home/user/RUST/libc)
    Finished dev [unoptimized + debuginfo] target(s) in 3.88s

user@openbsd64 ~/RUST/libc $ cargo build --release
   Compiling libc v0.2.46 (/home/user/RUST/libc)
    Finished release [optimized] target(s) in 2.21s

user@openbsd64 ~/RUST/libc/libc-test $ cargo test
   Compiling proc-macro2 v0.4.24
   Compiling unicode-xid v0.1.0
   Compiling semver-parser v0.7.0
   Compiling serde v1.0.84
   Compiling libc v0.2.45
   Compiling num-traits v0.2.6
   Compiling ryu v0.2.7
   Compiling cfg-if v0.1.6
   Compiling itoa v0.4.3
   Compiling term v0.4.6
   Compiling bitflags v0.9.1
   Compiling cc v1.0.28
   Compiling libc v0.2.46 (/home/user/RUST/libc)
   Compiling log v0.4.6
   Compiling semver v0.9.0
   Compiling log v0.3.9
   Compiling rustc_version v0.2.3
   Compiling rand v0.4.3
   Compiling extprim v1.6.0
   Compiling quote v0.6.10
   Compiling syn v0.15.23
   Compiling serde_derive v1.0.84
   Compiling syntex_pos v0.59.1
   Compiling serde_json v1.0.34
   Compiling syntex_errors v0.59.1
   Compiling syntex_syntax v0.59.1
   Compiling ctest v0.2.8
   Compiling libc-test v0.1.0 (/home/user/RUST/libc/libc-test)
    Finished dev [unoptimized + debuginfo] target(s) in 2m 16s
     Running /home/user/RUST/libc/target/debug/deps/linux_fcntl-08861a7cd96d1b94
RUNNING ALL TESTS
PASSED 0 tests
     Running /home/user/RUST/libc/target/debug/deps/main-57e266d38aa58cce
RUNNING ALL TESTS
PASSED 7187 tests
```
I've tried running the tests on a NetBSD 8.0 box unfortunately there `libc-test` fails to compile even before this change.

NetBSD 8 adds new address family changing AF_MAX and new ifaddrs flags.

libc-test on NetBSD 8.0  fails without these changes.
ifa_addrflags was added to struct ifaddrs to support AF_CAN.
AF_MAX got bumped up one by AF_CAN.
RT_IFLIST format changed to support ifa_addrflags.