* mpw-configure: Add more things to the top of each configured
Makefile, including contents of config/mpw-mh-mpw.
* mpw-config.in (extra-include): Create this directory and fill it
with Posix-like include files when configuring.
* mpw-build.in: New file, top-level build script fragment for MPW.
* mpw-configure: New file, configure script for MPW.
* mpw-config.in: New file, config fragment for MPW.