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

drivers/windows/dir_access_windows.cpp

@@ -33,7 +33,7 @@
 #include "dir_access_windows.h"
 
 #include "core/os/memory.h"
-#include "core/print_string.h"
+#include "core/string/print_string.h"
 
 #include <stdio.h>
 #include <wchar.h>