[CMake] Suggesting to FindQT4.cmake where to find QT4

[David Thompson]

> > Have you ever tried setting the PATH?  It is actually quite easy and does
> > not involve "great contortions".
> > 
> > All I do is execute
> > 
> > PATH='/home/software/qtsdk-2009.02/qt/bin:'$PATH
> > 
> > and from then on, cmake uses the version of Qt4 that I downloaded and
> > installed in the specified location.  If I want the system version of Qt4
> > again (which I don't for my needs), I remove the above from my PATH.
> 
> The issue is obviously what happens as soon as there are two independent
> libraries that are both so selfish.  Reylying on PATH being set up
> specially for you is terrible design unless you can guarantee that there
> will never be another.

Perhaps there is a miscommunication here; I think Alan is assuming that
you install at least one (if not all) versions of Qt into their own
directories (with no other software
in /home/software/qtsdk-2009.02/qt/bin except Qt) while you are assuming
that multiple packages are being installed into the same directory tree.
Doing things the former way, you can have as many of these entries in
your path as you like and there will never be a conflict among packages
because each PATH entry only points to a single package.

	David