Include <inttypes.h>, needed for <libutil.h> types

Wrap the extra includes in #ifdef for darwin
Make sure that <sys/stat.h> is being included

Wrap the extra includes in #ifdef for darwin
Add compat library for Darwin
Initial port to Darwin (Mac OS X)

Using a DARWIN make variable, and the built-in __APPLE__
macro. Requires CC=clang due to the anonymous unions.
The mach-o alternative to elf is just a stub for now.
Ignore shared libraries on Darwin
Add simple build script, with make options

Besides the required flags for make, also document the
various library dependencies (not handled at the moment).