Made PND_setwindowgrab() a no-op. It was a cut/paste of PND_destroywindow().

This looks like the rest of the code doesn't deal with windows, and probably
 just deals with a single fullscreen GLES context, like a console would, so
 making setwindowgrab a no-op makes sense in this case; it's already "grabbed."

Fixes Bugzilla #1850.

--HG--
extra : rebase_source : 29b07b9c8378f69fb8b5f201584befd8d7f005dd