Add musl support for MIPS64 & bump to 0.2.63

Tested with patched stage2; both static and dynamic binaries confirmed working.

Initial CI support in the form of no-core targets are added.

Add ioctl() constants for BPF

Update newlib socket types to FreeBSD

None

Rename armv7-wrs-vxworks target

Remove unnecessary trailing semi-colon

libc currently denies all warnings by default. This commit denies
warnings only when libc is built in CI.

add support for sparc64 on OpenBSD

Fix FreeBSD

#1440 broke FreeBSD by changing `libc` FreeBSD targets to require a `cfg(freebsdXX)` to be defined, but not updating `build.rs` to define `freebsd11` when `LIBC_CI` is not available. Since `LIBC_CI` is always defined on CI, this issue went undetected.

This PR fixes that issue in the `build.rs` and introduces a build task that tests FreeBSD without `LIBC_CI` on FreeBSD11, although I'm  not sure this would have caught the issue in #1466 .

Closes #1466 .

Update links

Update README Azure badge to rust-lang2 org

Bump version to 0.2.61

Releasing a version now will allow Redox compilation to work again, as it will include #1438

Add support for FreeBSD CURRENT (aka freebsd13)

Using the last FreeBSD-CURRENT (development snapshot) the libc build, but tests fail.
This patch detects and supports FreeBSD CURRENT as freebsd13, and reworks the conditional compilation to use the `freebsd11` attribute instead of `not(freebsd12)`
For now, freebsd13 is reusing all freebsd12 definitions, except for `ELAST`
While here, add a new `errno`introduced in freebsd13

Move musl-compatible constants to linux/mod.rs

This is a continuation of #1452. I think CI is ready to run fully and the PR is ready to be merged if the pipelines pass based on the CI I've done using musl libc in my own projects.

Support Vxworks

Define the C interface to VxWorks

Define the C interface to vxWorks for x86, x86_64, ARM, ARM 64-bit, PowerPC, PowerPC SPE and PowerPC 64-bit.

Upgrade FreeBSD's CI image to release 11.3

skip roundtrip on few structs on OpenBSD

skip roundtrip on some structs on OpenBSD. it is mostly the same than other targets: dirent, utsname, utmp.