Adding `wcsrtombs`.

Closes #166

See merge request redox-os/relibc!388

fix tzset cbindgen declarations

See merge request redox-os/relibc!386

Fix mspaces not being protected by locks.

See merge request !387

termios adding cfsetspeed bsd extension which set both __c_ispeed/__c_ospeed fields

See merge request !385

Fix platform::errno = ... in signal.rs

See merge request !384

signal add fewer more implementations

See merge request !378

setsid implementation

See merge request !381

cfmakeraw implementation proposal

See merge request !382

Add no-op tzset, plus required static vars

See merge request !383

fix no_mangle annotation missing

See merge request redox-os/relibc!377

signal add few missing implementations

See merge request !376

sync implementation

See merge request redox-os/relibc!375

unistd: fdatasync implementation.

See merge request !373

stdlib: unlockpt implementation proposal

See merge request !372

sys_resource: get/setpriority implementations.

See merge request !369

stdlib: getsubopt implementation proposal.

See merge request !371

sys_mman: adding madvise.

See merge request !370

Fix typos in setrlimit

See merge request !368

sys_resource: setrlimit implementation proposal.

See merge request !366