Entity support, doctype is not a tag

lib/ace/mode/xml_highlight_rules.js

@@ -59,13 +59,22 @@ var XmlHighlightRules = function() {
             merge : true,
             regex : "<\\!--",
             next : "comment"
+        }, {
+            token : "xml_pe",
+            regex : "<\\!.*?>"
         }, {
             token : "meta.tag", // opening tag
             regex : "<\\/?",
             next : "tag"
+        }, {
+            token : "entity",
+            regex : "&.*;"
         }, {
             token : "text",
             regex : "\\s+"
+        }, {
+            token : "entity.reference",
+            regex : "(?:&#[0-9]+;)|(?:&#x[0-9a-fA-F]+;)|(?:&[a-zA-Z0-9_:\\.-]+;)"
         }, {
             token : "text",
             regex : "[^<]+"