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

modules/webp/image_loader_webp.cpp

@@ -32,7 +32,7 @@
 
 #include "core/io/marshalls.h"
 #include "core/os/os.h"
-#include "core/print_string.h"
+#include "core/string/print_string.h"
 
 #include <stdlib.h>
 #include <webp/decode.h>