[Ohrrpgce] SVN: teeemcee/11225 gfx_sdl2: Fix mouse wheel not working

[subversion at HamsterRepublic.com]

teeemcee
2019-08-10 20:35:29 -0700 (Sat, 10 Aug 2019)
222
gfx_sdl2: Fix mouse wheel not working

But I worry that this breaks if you have a high-res mouse wheel. I expected
SDL2 to pre-multiply the amount of wheel movement, like the winapi does, to make
different mice comparable.
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U   wip/gfx_sdl2.bas