* mpw-make.in (MacGDB): New target, standalone Mac-hosted gdb.
(XDEPFILES): Define.
(main.c.o): Compile with gC instead of C.
* mac-defs.h: New file, menu etc definitions shared between
C and Rez files.
* macgdb.r: New file, Rez (resource compiler) resource
definitions.
* mac-xdep.c: New file, Mac host interface code.
* config/m68k/xm-mpw.h (PATHNAME_SEPARATOR): Rename to
DIRNAME_SEPARATOR.
(PATHNAME_SEPARATOR_STRING): Remove.
(SIGQUIT, SIGHUP): Define.
(fileno, R_OK): Define.
