Bindings: F11 by default will bind to togglefullscreen/releasemouse

Historically F11 has cycled through software gamma modes, but given
the "vid-gamma" cvar and the control panel, it seems unnecessary to
reserve a function key just for the software gamma.

Now F11 will toggle fullscreen mode, and Alt-F11 will release the mouse.

doomsday/plugins/common/src/g_controls.c

@@ -399,7 +399,9 @@ D_CMD(DefaultGameBinds)
         "bindevent shortcut:key-f8 {toggle msg-show}",
         "bindevent shortcut:key-f9 quickload",
         "bindevent shortcut:key-f10 quit",
-        "bindevent shortcut:key-f11 togglegamma",
+        //"bindevent shortcut:key-f11 togglegamma",
+        "bindevent shortcut:key-f11+key-alt-down releasemouse",
+        "bindevent shortcut:key-f11 togglefullscreen",
         "bindevent shortcut:key-print screenshot",
         "bindevent shortcut:key-f12 screenshot",