Build: Explicitly include ppsspp_config.h.

This adds it to all files that use it.  Not all our builds include the
file.

UI/ControlMappingScreen.cpp

@@ -15,6 +15,7 @@
 // Official git repository and contact information can be found at
 // https://github.com/hrydgard/ppsspp and http://www.ppsspp.org/.
 
+#include "ppsspp_config.h"
 #include <algorithm>
 #include <deque>
 #include <mutex>