Fixed compile (for certain configurations)

Fixed compile (for certain configurations)

This project tried to use libQtTest, but omitted `QT+=testlib'.

In most configurations, this didn't matter, because:

  - for includes, QtQuickTest has copied the content of some QtTest
    headers, instead of #including them, so the bad INCLUDEPATH went
    unnoticed

  - for libraries, libQtTest would be pulled in implicitly either via
    .prl files or via the system's linker, so the bad LIBS went
    unnoticed

Change-Id: Ie3286718789758bfb80f6832aac7c08bdd85212a
Reviewed-on: http://codereview.qt.nokia.com/1812
Reviewed-by: Jonni Rainisto <jonni.rainisto@nokia.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@nokia.com>
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>