Closes #736

Add QCMD() for available platforms

Exists where `Q_QUOTAON` also exists, so added it for those same platforms.

Add QFMT_VFS_V1 on MIPS and test all QFMT_ constants

Bump to 0.2.30

Updated types of PTRACE requests for musl to be consistent.

For some reason the type of ptrace request constants in musl change for the register based requests. As they are used in the same way and this doesn't mimic musl this has been changed for consistency and ease of use.

First raised in issue #744

Add asmjs/wasm32 to CI

Rebase of #610 and also move emscripten up much higher in the hierarchy to
ensure that it doesn't have too much of a ripple effect on other platforms.

This involved moving down a good number of definitions, but hopefully was done
with care to not break anything!

Add syscall constants to more Android/Linux targets

Primarily adding `SYS_memfd_create` and `SYS_pivot_root` for `nix`. But I also equalized a few constants across platforms so some of the other ones that were defined on some targets are now defined across all linux/android targets.

For some reason the type of ptrace request constants in musl change for the register based requests. As they are used in the same way and this doesn't mimic musl this has been changed for consistency and ease of use.

Rebase of #610 and also move emscripten up much higher in the hierarchy to
ensure that it doesn't have too much of a ripple effect on other platforms.

This involved moving down a good number of definitions, but hopefully was done
with care to not break anything!

haiku: Add missing signals

* Now a complete signal list on Haiku minus reserved.
* Fixes build failure due to missing SIGUSR1

* Now a complete signal list on Haiku minus reserved.
* Fixes build failure due to missing SIGUSR1

Add {,f}stat{,v}fs64 API bindings

Closes https://github.com/rust-lang/libc/issues/738

haiku: Correct typo

Add more fcntl and seal constants for Android/Linux

Add more fcntl constants for android

This works by specifying a "runner" for actually executing the binary.
This doesn't apply to the Android or NetBSD runs because there
isn't a simple binary that just runs the executable.

We now create an additional binary `linux_fcntl` for testing this
since there are header conflicts when including all necessary headers.
This binary is run on all platforms even though it's empty on all non-
Android/non-Linux platforms.

Testing has been switched from a custom binary to using a runner-less
test (or pair of tests). This means that for local development a simple
`cd libc-test && cargo test` will run all the tests. CI has also been
updated here to reflect that.

Fix spelling of ptrace's request argument

Couldn't handle seeing this anymore after working on a ptrace API for `nix`!

L4Re improvements

This commit improves the x86_64 uClibc port and splits of L4Re-specific structs into a separate submodule. It defines additional constants and fixes some unfinished structs.

Remove OpenBSD CI

It's now broken due to changes in the `gcc` crate and having a too-old compiler,
and in general it's unfortunately architecturally so different from the other
test frameworks that it's difficult to maintain over time.

It's now broken due to changes in the `gcc` crate and having a too-old compiler,
and in general it's unfortunately architecturally so different from the other
test frameworks that it's difficult to maintain over time.