Turns the two set of tables in QDrawHelperGammaTables into two
QColorProfile classes that use similar structures and can be reused for
other gamma correction.
At the same time clean-up and improve the comma-correct blending code
to use the new profiles and QRgba64 precision.
Change-Id: I302bd87a5c836e1010fff6d633eeb56fd4ae2ff0
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>