Remove support for XFree8-4.
From now on, X_WINDOW_SYSTEM != "xorg" is not supported anymore.
PR: ports/119418
Submitted by: flz
Approved by: portmgr (pav)
[1] Make the HTML manpages get put into the packages again.
[2] Check that XFREE86_VERSION=4 is set when building, rather than setting it.
[3] Move many common Makefile bits to XFree86-4-libraries/Makefile.inc
[4] Make the XFree86-4-Server port not install libXfont.so.
[5] Move the xcursor.pc file to its proper location in
${X11BASE}/libdata/pkgconfig
[6] Don't explicitly link libGL.so against libc, for the sake of 4.x's pthreads.
Submitted by: [5,6] Ports Fury