Change the handling for windowing system specific files so that
when building for more than one set, each gets compiled as a set
instead of some being interspersed among rival window systems.
Put differently, handle tile.o specially so that there's no need
for the hints to sort the WINOBJ list in order to avoid tile.o
duplication.
So the order of compilation is
common source files
unix-specific files
tty files
curses files
X11 files
Qt files
tile.c (if applicable), version.c, date.c
Previously, some of the X11 files were scattered around among the
others because of the spelling of their file names.
Only matters if you're watching the progress of a build.
4de71302a3