[Ohrrpgce] SVN: teeemcee/12435 gfx_sdl2: fix window moving to 0, 0 when unfullscreening if you change zo

[subversion at HamsterRepublic.com]

teeemcee
2021-09-14 07:53:43 -0700 (Tue, 14 Sep 2021)
508
gfx_sdl2: fix window moving to 0,0 when unfullscreening if you change zoom while fullscreen on Windows

I originally had a much more complicated fix for this bug which I spent far too
long on which fixed the bug on Windows and caused an identical bug to occur on
Linux, which I gave up on fixing! I didn't realise that I hadn't actually
accomplished anything until it was time to write the commit message!

Also, actually call SDL_SetWindowSize immediately when restoring the size,
seemingly no reason not to
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U   wip/gfx_sdl2.bas