Separate the compiler flags used for compiling X11 code from the rest
of CFLAGS. Affects hints/macosx10.8 and later.
Add an explicit output argument to the generated compile rules.
The change to Makefile.src for X11+XPM on linux broke linking X11 on
OSX. This updates the hints files (except for the -qt one) so that
make WANT_WIN_X11=1
and
make WANT_WIN_X11=1 USE_XPM=1
work correctly.
The comment in macosx10.14 about what version(s) it's intended for
and been tested on is just cloned from 10.10 and should be updated.
