Make isDown accept a list of keys (issue #121)

src/modules/keyboard/sdl/Keyboard.h

@@ -46,7 +46,7 @@ namespace sdl
 		* @param key A key identifier.
 		* @return boolean
 		**/
-		bool isDown(Key key) const;
+		bool isDown(Key * keylist) const;
 
 		/**
 		* Enables key repeating.
@@ -78,4 +78,4 @@ namespace sdl
 } // keyboard
 } // love
 
-#endif // LOVE_KEYBOARD_SDL_KEYBOARD_H
+#endif // LOVE_KEYBOARD_SDL_KEYBOARD_H