[Ohrrpgce] SVN: teeemcee/11713 Optimise 8-bit blending by using alpha_blend; moved to blend.h

[subversion at HamsterRepublic.com]

teeemcee
2020-04-08 20:27:16 -0700 (Wed, 08 Apr 2020)
263
Optimise 8-bit blending by using alpha_blend; moved to blend.h

I merged the code from the blit.c and surface.h routines.

Just because alpha_blend is now inlined, 32-bit blending is also almost 2x faster
Fast dithering is now up to 20x faster than slow dithering
---
A   wip/blend.h
U   wip/blit.c
U   wip/ohrhelp/sliceedit_blend_algo.txt
U   wip/slices.bas
U   wip/surface.cpp
U   wip/surface.h