Add entity for Enum synopsis

Author: Girgias

language-defs.ent

@@ -86,6 +86,7 @@ supplemental files to mark section titles -->
 <!ENTITY reftitle.changelog    '<title xmlns="http://docbook.org/ns/docbook">&Changelog;</title>'>
 <!ENTITY reftitle.classes      '<title xmlns="http://docbook.org/ns/docbook">Predefined Classes</title>'>
 <!ENTITY reftitle.classsynopsis '<title xmlns="http://docbook.org/ns/docbook">Class synopsis</title>'>
+<!ENTITY reftitle.enumsynopsis '<title xmlns="http://docbook.org/ns/docbook">Enum synopsis</title>'>
 <!ENTITY reftitle.constants    '<title xmlns="http://docbook.org/ns/docbook">Predefined Constants</title>'>
 <!ENTITY reftitle.constructor  '<title xmlns="http://docbook.org/ns/docbook">Constructor</title>'>
 <!ENTITY reftitle.description  '<title xmlns="http://docbook.org/ns/docbook">Description</title>'>