calling uname(3) can find out what os it is running on. Tested only with a
bsdi binary that calls getkerninfo directly. Funny thing is that I ran
the same binary on a bsdi machine, and they fill in fewer fields in the
emulation than we do; maybe I went overboard :-)
- Created compat_util.c and compat_util.h to be used by the compatibility
modules, so they don't duplicate the same code.
- Added prototypes to the stackgap allocation routines.