build config.h, add empty definitions to mk.tmp.
(powerpc-apple-macos): Make it work.
* mpw-make.sed: New file, sed commands to translate Unix makefile
into MPW syntax.
* mpw-make.in: Remove.
* mac-gdb.r: New file, was macgdb.r, renamed for consistency
with other tools, now includes cfrg resource.
* macgdb.r: Remove.
* config/m68k/xm-mpw.h: Remove most of contents, replace with
include of include/mpw/mpw.h.
