Refactor readUTF8Char into charmap_ConvertNext

include/util.hpp

@@ -3,13 +3,6 @@
 #ifndef RGBDS_UTIL_HPP
 #define RGBDS_UTIL_HPP
 
-#include <stddef.h>
-#include <stdint.h>
-#include <vector>
-
 char const *printChar(int c);
 
-// @return The number of bytes read, or 0 if invalid data was found
-size_t readUTF8Char(std::vector<int32_t> *dest, char const *src);
-
 #endif // RGBDS_UTIL_HPP