Support for Unicode XML/HTML identifiers

Technically HTML only allows for ASCII names but restricting that
actually requires more work than just allowing it.

ext/ragel/base_lexer.rl

@@ -48,7 +48,9 @@
 
     newline    = '\r\n' | '\n' | '\r';
     whitespace = [ \t];
-    ident_char = [a-zA-Z0-9\-_\.];
+
+    unicode    = any - ascii;
+    ident_char = unicode | [a-zA-Z0-9\-_\.];
     identifier = ident_char+;
 
     whitespace_or_newline = whitespace | newline;