Proposed changes to FindQt4.cmake

[Caleb Tennis]

Please see the attached patch for FindQt4.cmake.

The problem is with Qt4 installed as a framework on OSX.  Since  
apparently FIND_LIBRARY doesn't work, the framework information and  
paths are just hardcoded.  This is a problem if those libraries don't  
exist.  As is, things like QT_QTXXX_FOUND aren't valid for this type  
of installation and so using them to make determinations doesn't work.

This patch fixes that.  It sets the proper FOUND variables as well as  
the LIBRARY variables only if the corresponding libraries are found.

I can commit, but I'd like to make sure nobody objects.

Caleb