[Ohrrpgce] SVN: teeemcee/11714 Remove blendAlgoDitherSlow, instead add blendAlgoLessDither

[subversion at HamsterRepublic.com]

teeemcee
2020-04-08 22:56:17 -0700 (Wed, 08 Apr 2020)
359
Remove blendAlgoDitherSlow, instead add blendAlgoLessDither

There was no point having slow dithering that was so much slower and very hard
to see any improvement.
On the other hand, 'Less dither' (1/4 instead of 5/8 error diffusion) is a
compelling option.

To compensate, doubled the size of nearcolor_cache to 64KB, which caused a
miniscule speed reduction
---
U   wip/blit.c
U   wip/ohrhelp/sliceedit_blend_algo.txt
U   wip/sliceedit.bas
U   wip/surface.bi
U   wip/surface.h
U   wip/whatsnew.txt