Simplify GL2PaintEngine::updateTextureFilter, it doesn't need target

Change-Id: I8b71c33adb37c166bf4fc6dc8c2e7418d60fbf81
Reviewed-by: Laszlo Agocs <laszlo.agocs@theqtcompany.com>
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@theqtcompany.com>
qmake: Add .qmake.stash/super to QMAKE_DISTCLEAN when owned by project

Running 'make distclean' should remove all files generated by qmake,
including .qmake.stash/super. These files are considered owned by
a particular project (and hence a candidate for distclean), if it
lives in the same directory as the output dir of the project.

Task-number: QTBUG-42678
Change-Id: I224e9bac039eeacb6561e18acc7f8e867da5dab8
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@theqtcompany.com>