redundant files from platform directories. (Yes, we already have
"pdcurses", but that's for the portable core; "common" is for files that
are more platform-specific, though shared by more than one platform.)
compiler, and YYY was the platform -- which was redundant with the
directory name. This way, the makefiles sort together, apart from the
source files. It also lets me drop the extension on one of them for each
port, so that one can be used without "-f". (I chose gcc for this,
somewhat arbitrarily.) Inspired by contemplating the renaming of
"win32".
