patch to unhook libxpg4 and liby from build

[Chris Pressey]

Howdy once again,

There's an afwul lot of good build re-engineering going on lately, and I
wanted to contribute a tiny bit to it.  I was looking through src/lib
and found two libraries that appear to be obsolete (as they are
essentially empty,) libxpg4 and liby.  So, I unhooked them from my
build, and as I suspected, everything still builds fine.  The (small)
patch to achieve this is here:

http://catseye.webhop.net/DragonFlyBSD/patch/unhook_libxpg4_liby.diff

If someone can confirm that these libraries really are really and truly
100% obsolete, I'll enqueue the patch.

-Chris