x11-links creates a shadow directory of symbolic links for X11 headers and
libraries to ${X11BASE} under ${LOCALBASE}/share/x11-links.  It is intended
for use by buildlink code to cleanly separate out the true X11 code files
from any installed X11 package code files.  The X11 hierarchies supported
are:
	XFree86-3.3.x
	XFree86-4.0.x
	XFree86-4.1.x
	XFree86-4.2.0