Add a workaround for disk space failures on Docker

Add CPU_ALLOC_SIZE

Co-Authored-By: Yuki Okushi <huyuumi.dev@gmail.com>

freebsdlike: add SCM_CREDS, struct sockcred

Like on NetBSD, but without a pid field in the struct.

It is present on both FreeBSD and DragonFly

Add CPU_COUNT/CPU_COUNT_S

revenge of #598

Add `rtentry` to musl

REG_ENOSYS is NetBSD specific

Set rustup profile to minimal on Windows

Minor clean-up CI docs

Bump version to 0.2.69

Enable `wasm32-unknown-emscripten` target on CI

Remove license headers

Add bindings for POSIX regexes

Headers I used:

Oh, for reference, here are the headers I used while working on this:

- musl: https://git.musl-libc.org/cgit/musl/tree/include/regex.h?id=8327ae0cb23b799bc55a45e0d4bd95f5a2b1cdf1
- glibc: https://sourceware.org/git/?p=glibc.git;a=blob;f=posix/regex.h;h=87cce7f5cb8cc3b678467329b479bd511e250e61;hb=HEAD
- macOS: https://opensource.apple.com/source/Libc/Libc-997.90.3/include/regex.h.auto.html
- FreeBSD: https://github.com/freebsd/freebsd/blob/8103b0ddb041617b7cd161528f0ff93ff32970a2/include/regex.h
- NetBSD: https://github.com/NetBSD/src/blob/61c8f6fbb7e38b20e862d5cb3ed2203312963283/include/regex.h