fix so ./faketime is not a library
Assume system being little endian on __APPLE__
Fix missing clock_gettime() related #defines on __APPLE__
Don't use a = {b,c} assignment
Prevent applying time faking mote than once
Improved OS X support

Conflicts:
	src/libfaketime.c
Default to clang on __APPLE__ to support thread local variables
Fix compilation on __APPLE__
Fake clock_get_time() on __APPLE__
Sleep() and alarm() still could apply faking several times
merged rbalint's pr27