Fix QT4 moc, cflags libs detection on dual QT3/Qt4 systems

On system with QT3 and QT4 qmake in PATH may be from QT3. So we use
pkg-config for proper QT4 detection.
By reqesting cflags and libs for either QtCore, QtGui and QtSupport include
dirs and libs get listed several times, but so we won't mis anything

Signed-off-by: Alexander Stein <alexander.stein@informatik.tu-chemnitz.de>
Acked-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Michal Marek <mmarek@suse.cz>