sys/mman.h update addinng mlockall and posix_madvise flags

See merge request !357

wctrans/towctrans implementation proposal.

Closes #32

See merge request redox-os/relibc!356

close #32

reallocarray introduction available on glibc 2.26. allocates an array of m*n...

See merge request !355

adding SOCK_RDM and a couple of POLL* constants.

Closes #164

See merge request !354

reallocarray introduction available on glibc 2.26. allocates an array of m*n elements but checking for overflow.

close #164

strlcpy/strlcat api for portability's sake.

See merge request !353

those functions differently than the strn* ones as
they do not pad with zero to remaining bytes but guarantees
a null terminator.

explicit_bzero implementation proposal

See merge request !337

Provide possible fix for `x86_64-linux-gnu-ar: command not found` (or similar) in README.md

See merge request redox-os/relibc!351

Fix definition of `wcstombs`

See merge request redox-os/relibc!350