We are in a situation now with the migration to Xfree-4 that causes 2
problems.

1)  PLIST issues.  I recently noticed that for a particular package I got
a different PLIST depending on if I was on a Xfree-3 machine (all non-i386
and some i386) vs. a Xfree-4 machine.  In this case it was the Xft and
Xrender libraries which come with Xfree-4 which caused extra stuff to be
built and installed.  I wonder if we need a bsd.lib.mk check for Xfree-4
that would set some variable that a package should check for to add a
PLIST.XF4 to PLIST_SRC?  

2)  Binary package incompatibility.  Binary packages built on XFree-4
boxes are not compatible with binary packages built on XFree-3 boxes.
This is partly due to different dependencies, for example Xpm is builtin
for Xfree-4 but not for Xfree-3, and partially due to different shared
library version numbers in Xfree-4 vs Xfree-3.  Perhaps we need to store
the bit of info that a package was built on an XFree-4 box vs XFree-3 box
and do some error checking in pkg_install?  This would be similar to the
test which should be added to prevent accidental installation of a vax
binary package on a sparc.

Thoughts?

-Dan