client: avoids vid_restart if win didn't resize

On OS X at least, it's possible to receive a resize event when the window simply moves, or even when Dock shows/hides. No need to do a vid_restart then, so it does a simple check.
Merge branch 'master' of https://github.com/swillits/etlegacy

(I'm not very good at git!)

* 'master' of https://github.com/swillits/etlegacy:
  client: avoids vid_restart if win didn't resize

Conflicts:
	src/sdl/sdl_input.c