Codechange: Consistently use WChar when passing characters around, and also define it as char32_t.

src/string_type.h

@@ -32,7 +32,7 @@ enum CharSetFilter {
 };
 
 /** Type for wide characters, i.e. non-UTF8 encoded unicode characters. */
-typedef uint32 WChar;
+typedef char32_t WChar;
 
 /* The following are directional formatting codes used to get the LTR and RTL strings right:
  * http://www.unicode.org/unicode/reports/tr9/#Directional_Formatting_Codes */