sw_engine raster: fix a crash at the texmap clipping.

sw_engine raster: fix a crash at the texmap clipping.

Handle correctly duplicated spans from the multiple y span data.

Previous logic only expected the one single y span data from the rle.
However rle might have multiple y span data if the anti-aliasing is applied.

This patch also removed the bad design of the common engine
which handles the anti-alising option to ignore the anti-aliasing rle generation.

Just realized, it's difficult to control that condition due to scene-composition.

Change-Id: I0caab0e22b0bb88bf0c7ed25b58229c216579086