Disable OSX app nap

This will hopefully help deal with a particular issue where the program
may go to sleep if it hasn't received input from the user for long
periods, or if a game is running in fullscreen mode apparently.

cmake/osxbundle/Info.plist

@@ -20,5 +20,7 @@
 	<string>10.8.5</string>
 	<key>NSHighResolutionCapable</key>
 	<true/>
+	<key>LSAppNapIsDisabled</key>
+	<true/>
 </dict>
 </plist>