initial ARB FP drawing

- only does RGB32 (just like msink in pgst)
- only can do aspect retaining scaling (just like before)
- ludicrous design (literally not existant actually), final design will
probably assume a mixture of qtquick2 like surfaces and various painter
implementations (we need at least raster and GSLS, and since it is now
around anyway ARB - perhaps something X too?)

by default we render using raster, if gl is available and PHONON_PAINT
is set to either gl (which paints using qimage texture upload thru
qlcontext) or directgl (which uses the ARB shader program)

for testing you could for example run:
export PHONON_PAINT=directl
qmlviewer -opengl videoplayer.qml