Sync to rust-lang/libc branch master

VxWorks libc cleanups and fixes for some libc-test issues

move rtpSpawn and RTP_ID_ERROR from libstd to libc

use union for unions

Add environment variable FILTER to choose which target(s) to run

Skip max_align_t in FreeBSD10

This error was able to land because FreeBSD10 is not checked by bors yet (see: RCS PR: https://github.com/rust-lang/rust-central-station/pull/481) .

Fixes

Two patches fixing minor issues.

Add FreeBSD10 support

This adds libc-test support for Freebsd10 and a CI build job that tests
FreeBSD10 with LIBC_CI only.

cc @asomers this is a follow up to #1491 .

VxWorks libc cleanups and fixes for some libc-test issues that were p…

Implement max_align_t

Implement `max_align_t` for windows and unix targets.

WIP: at this stage I just want to see what breaks.

pthread_exit return type fix

Closes: #1520

Sync to rust-lang/libc branch master

Re-enable all roundtrip tests

Signed-off-by: Philipp Gesang <phg@phi-gamma.net>

It's *msg_prio* in both manpages and posix.

Fix building error at backtrace

I get this error when builind backtrace:

error[E0308]: mismatched types
  --> /folk/prj-rust-dev/bpang/ala-diab-pb19l/fix_bugs/latest/.cargo/git/checkouts/backtrace-rs-fb1f822361417489/e745627/src/symboli\
ze/dladdr.rs:38:73
   |
38 |                         Some(SymbolName::new(slice::from_raw_parts(ptr, len)))
   |                                                                         ^^^ expected usize, found u64
help: you can convert an `u64` to `usize` and panic if the converted value wouldn't fit

It shows the 'size_t' is expected to be defined as "usize".

defining uintptr_t = usize and intptr_t/ptrdiff_t = isize, and using uintptr_t to define size_t, and intptr_t to define ssize_t.

Sync with rust-lang/libc branch master

updates for vxworks

fix problems found in testing
VxWorks socket and epoll definitions needed by mio and related crates; epoll only supported in VxWorks kernel; just provide stub definitions for user mode for now
Fixed usage of isize
libc VxWorks cleanups and additions
remove copyright notice

2. implement Debug for big size array
3. remove code related to epoll
4. use 'pub enum' for _Vx_semaphore

This adds libc-test support for Freebsd10 and a CI build job that tests
FreeBSD10 with LIBC_CI only.

add isblank

Fixes #1509