"vid_restart partial" only changes the window size or its fullscreen
(or windowed) state, without recreating everything.
If that fails (or antialiasing settings have changed), it will fall back
to a full vid_restart (this behavior is different than original
"vid_restart partial" that probably was implemented in Vanilla Doom3
but not dhewm3)
This is used for Alt-Enter (which toggles between fullscreen and
windowed state) and when pressing the Apply button in the new Video Menu
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