(core+) blend fix, dirty tracking fix++

Refactoring gl support is now leaving the _video.c
with frameserver + 3dbase left along with the
usual clamping down on regressions. There are things
missing in the platform layer still (particularly
gles3 implementation, vstore/rendertarget canvas resize)
along with possible issues with push/pop ext.
Still this the more difficult and comprehensive layer
refactoring seems to be possible to clear this week.