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

platform/linuxbsd/detect_prime_x11.cpp

@@ -33,8 +33,8 @@
 
 #include "detect_prime.h"
 
-#include "core/print_string.h"
-#include "core/ustring.h"
+#include "core/string/print_string.h"
+#include "core/string/ustring.h"
 
 #include <stdlib.h>