Use loc::toupper_ch instead of SDL_toupper in VFormat

This commit is part of rewritten history of the localization branch.
The original (unsquashed) commit history can be found here:
https://github.com/Dav999-v/VVVVVV/tree/localization-orig

desktop_version/src/CWrappers.cpp

@@ -1,8 +1,12 @@
 #include <SDL.h>
 
+#include "Localization.h"
 #include "UtilityClass.h"
 
-extern "C" char* HELP_number_words(int _t)
+extern "C"
+{
+
+char* HELP_number_words(int _t)
 {
     /* C wrapper for UtilityClass::number_words.
      * Caller must VVV_free. */
@@ -15,3 +19,10 @@ extern "C" char* HELP_number_words(int _t)
 
     return buffer;
 }
+
+uint32_t LOC_toupper_ch(uint32_t ch)
+{
+    return loc::toupper_ch(ch);
+}
+
+} /* extern "C" */