disable printing times on !__MACH__

We disabled collecting process-level statistics in d0f35f6 anyway.
make sure __assert_rtn is compiled as extern "C"
hack in a version string for the linker
add md5 implementation
declare all output files as being mappable files
update the makefile for md5
add xnu constants to LinkEdit.hpp too

#include'ing AddressSpace.hpp here fails due to multiple-definition errors.
So we just redefine the constants here.
declare strl* in HeaderAndLoadCommands.hpp
make OutputFile.cpp use the included md5 implementation
include OutputFile.cpp in the sources
link ld64 with libuuid for uuid_generate_random
don't search for ld_classic relative to ld64

Just use $PATH instead.