Subpixel rendered text doesn't work in the old OpenGL paint engine
because it assumes the glyphs are returned in RGB32 format, when they
may be in ARGB32. This patch changes the test of the returned format
to just check for 32bit matching the logic in the new OpenGL paint
engine.

Change-Id: Ib5b784dedba51cf22f216e2f035361518610b96b
Reviewed-by: Laszlo Agocs <laszlo.agocs@theqtcompany.com>