Factor out an UpperMap for case-insensitive matching

include/util.hpp

@@ -3,9 +3,23 @@
 #ifndef RGBDS_UTIL_HPP
 #define RGBDS_UTIL_HPP
 
+#include <stddef.h>
+#include <string>
+#include <unordered_map>
+
+#include "helpers.hpp"
+
 bool startsIdentifier(int c);
 bool continuesIdentifier(int c);
 
 char const *printChar(int c);
 
+struct Uppercase {
+	size_t operator()(std::string const &str) const;
+	bool operator()(std::string const &str1, std::string const &str2) const;
+};
+
+template<typename T>
+using UpperMap = std::unordered_map<std::string, T, Uppercase, Uppercase>;
+
 #endif // RGBDS_UTIL_HPP