Re-enabled an old feature

A simple work, but necessary : I've finished to set the "force aspect ratio" feature. Now, when you draw a box, an ellipse or if you resize, simply hit the <CTRL> key to force the aspect ratio ; now, you can finally obtain direcly perfects squares and circles, not only rectangles/boxes or ellipses.
Here is a screenshot :

Note : only available on revision #38, you shall compile yourself or wait until 31 Janv 2012 for a .DEB package