EvasGL: Fixed direct rendering not clipping issue

EvasGL: Fixed direct rendering not clipping issue

Evas GL direct rendering mode didn't properly take into account
the image object's clipping information and clip the region that
it was directly rendering to. Hence there were issues with the
direct rendering region drawing over the objects that are sitting
on top of it.

Also, cleaned up the direct rendering coordinate computation code
and a nasty dependency with image object that should have been
removed a long time ago.  Basically the evas-gl engine was directly
accessing the image object data structure for its data when it
really should have just passed along necessary information.