Add utf-8 conversion utilities and re-add intlGUIEditBox

src/util/string.h

@@ -39,10 +39,18 @@ struct FlagDesc {
 	u32 flag;
 };
 
+// try not to convert between wide/utf8 encodings; this can result in data loss
+// try to only convert between them when you need to input/output stuff via Irrlicht
+std::wstring utf8_to_wide(const std::string &input);
+std::string wide_to_utf8(const std::wstring &input);
+
+// NEVER use those two functions unless you have a VERY GOOD reason to
+// they just convert between wide and multibyte encoding
+// multibyte encoding depends on current locale, this is no good, especially on Windows
+
 // You must free the returned string!
 // The returned string is allocated using new
 wchar_t *narrow_to_wide_c(const char *str);
-
 std::wstring narrow_to_wide(const std::string &mbs);
 std::string wide_to_narrow(const std::wstring &wcs);