OSX: Use MAP_ANON instead of MAP_ANONYMOUS.
OSX: Provide implementations of clock_gettime.
OSX: ENONET doesn't exist, EHOSTDOWN is the same.
OSX: Fix return value for CLOCK_REALTIME.
OSX: Don't cache clock service.

Caching the clock service makes it wonky when you fork(), as they are
per-process.
Merge branch 'osx-port' of https://github.com/jorgenpt/mek.lu into jorgenpt-osx-port

Conflicts:
	Makefile
Merge branch 'jorgenpt-osx-port'
OSX: Set appropriate errno in clock_gettime
Adjust the Makefile

Avoid calling uname twice. In addition, ISO C forbids empty
translation units, so we'll only compile clock.c when needed.
This prevents a -pedantic warning.