Revert "Tools: qmake: features: don't use gstreamer directly but through qtmultimedia"

This reverts commit 7a13237257c0d1e246fa6575c4d45d20bd30ce50.

Right now using qtmultimedia inbetween gives us too much problems. Overall the
qtmultimedia support within qtwebkit seems to be broken in several aspects so we're
switching back to let it use plain gstreamer.

Signed-off-by: Simon Busch <morphis@gravedo.de>