This patch updates the internal color precisions of solids and
gradients to 16bit per color. This makes it possible to render
at higher precision on non-premultiplied ARGB32, the RGB30
formats and any other hi-color formats if more are added.
[ChangeLog][QtGui][Painting] Internal precision of solids and gradients
is now up to 16bit per color.
Change-Id: Ieae5468bd6de1f56adfa4cb9fa966faf2ed824fd
Reviewed-by: Gunnar Sletta <gunnar@sletta.org>