[Ohrrpgce] SVN: teeemcee/9599 gfx_sdl2: Implement presenting of 8-bit surfaces. Now displays correctly

[subversion at HamsterRepublic.com]

teeemcee
2017-10-22 21:10:47 -0700 (Sun, 22 Oct 2017)
190
gfx_sdl2: Implement presenting of 8-bit surfaces. Now displays correctly, as long as smooth=0.

Zooming still isn't handled correctly, particularly when smoothing.

Also, added CheckOK macro
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U   wip/gfx_sdl2.bas