gtk targets and pkg-config

[Havoc Pennington <hp redhat com>]

Hi,

At the moment, "pkg-config --libs gtk+-2.0" returns libs for the
target GTK was compiled for. 

I think instead, "pkg-config --libs gtk+-2.0" should only work for the
X target, and "pkg-config --libs gtk+-linux-fb-2.0" should be required
for the FB target, etc. Since the headers are the same for all targets
(I think...) we can then install and use multiple targets
simultaneously, and you can also check for the proper GTK with 
"pkg-config --exists gtk+-linux-fb-2.0", etc.

Havoc