Reorganized core/ directory, it was too fatty already

-Removed FuncRef, since Callable makes it obsolete
-Removed int_types.h as its obsolete in c++11+
-Changed color names code

main/main_timer_sync.h

@@ -31,7 +31,7 @@
 #ifndef MAIN_TIMER_SYNC_H
 #define MAIN_TIMER_SYNC_H
 
-#include "core/engine.h"
+#include "core/config/engine.h"
 
 struct MainFrameTime {
 	float idle_step; // time to advance idles for (argument to process())