Refactored gl window surface a bit.
Refactored gl window surface a bit.

The logic was a bit messy and didn't work on Mac OS X. On Linux we also had issues
with 8xxx nvidia cards which didn't render properly.

The FBO is now unbound between calls to beginPaint(), which prevents other
gl calls from messing it up, which is probably what was the error in the first place.
In addition, on Mac OS X, we also call the upatePaintDevice() as a result of
setGeometry() to force-update the dimensions of the context.

Reviewed-by: Trond

radekp/qt,pruiz/wkhtmltopdf-qt,igor-sfdc/qt-wk,pruiz/wkhtmltopdf-qt,pruiz/wkhtmltopdf-qt,pruiz/wkhtmltopdf-qt,pruiz/wkhtmltopdf-qt,igor-sfdc/qt-wk,pruiz/wkhtmltopdf-qt,pruiz/wkhtmltopdf-qt,radekp/qt,igor-sfdc/qt-wk,radekp/qt,igor-sfdc/qt-wk,igor-sfdc/qt-wk,pruiz/wkhtmltopdf-qt,pruiz/wkhtmltopdf-qt,radekp/qt,igor-sfdc/qt-wk,radekp/qt,radekp/qt,igor-sfdc/qt-wk,pruiz/wkhtmltopdf-qt,igor-sfdc/qt-wk,radekp/qt,radekp/qt,radekp/qt,igor-sfdc/qt-wk,igor-sfdc/qt-wk,igor-sfdc/qt-wk,radekp/qt,pruiz/wkhtmltopdf-qt