Handle link tails properly.

- Added a tail json attribute for wikiLinks
- During serialization, this attribute is used to strip the tail from
  the link target and render it after the link

  [[hen]]s ==> <a ... data-mw="{gc:1, tail: 's'}" ...>hens</a>
           ==> [[hen]]s

- 2 more roundtrip tests green

Change-Id: I84f3dabaf0271f7a67641a00148467daa8310eb0

modules/parser/ext.core.LinkHandler.js

@@ -64,7 +64,7 @@ WikiLinkHandler.prototype.onWikiLink = function ( token, frame, cb ) {
 			obj.dataAttribs.gc = 1;
 		}
 		if ( tail ) {
-			// TODO: make this round-trippable
+			obj.dataAttribs.tail = tail;
 			content.push( tail );
 		}
 		

modules/parser/mediawiki.WikitextSerializer.js

@@ -121,6 +121,10 @@ WSP._linkHandler =  function( state, token ) {
 				);
 
 		if ( attribDict.rel === 'mw:wikiLink' ) {
+			if (token.dataAttribs.tail) {
+				state.linkTail = token.dataAttribs.tail;
+			}
+
 			if ( token.dataAttribs.gc ) {
 				return '[[';
 			} else {
@@ -153,8 +157,10 @@ WSP._linkEndHandler =  function( state, token ) {
 	var attribDict = state.env.KVtoHash( token.attribs );
 	if ( attribDict.rel && attribDict.href !== undefined ) {
 		if ( attribDict.rel === 'mw:wikiLink' ) {
+			var retVal = "]]" + (state.linkTail ? state.linkTail : "");
+			state.linkTail   = null;
 			state.dropContent = false;
-			return ']]';
+			return retVal;
 		} else if ( attribDict.rel === 'mw:extLink' ) {
 			if ( token.dataAttribs.stx === 'urllink' ) {
 				state.dropContent = false;
@@ -402,6 +408,7 @@ WSP._serializeToken = function ( state, token ) {
 			state.precedingNewlineCount = 0;
 		}
 		if ( ! dropContent || ! state.dropContent ) {
+			if (state.linkTail) res = res.replace(new RegExp(state.linkTail + "$"), "");
 			state.chunkCB( res );
 		}
 	}