Expose the comment tags known by the completion engine.

ICSharpCode.NRefactory.CSharp/Completion/CSharpCompletionEngine.cs

@@ -2988,6 +2988,12 @@ namespace ICSharpCode.NRefactory.CSharp.Completion
 		}
 		);
 
+		public static IEnumerable<string> CommentTags {
+			get {
+				return commentTags;
+			}
+		}
+		
 		string GetLastClosingXmlCommentTag()
 		{
 			var line = document.GetLineByNumber(location.Line);