add API procedure, Michael review

blocks.js

@@ -7558,12 +7558,11 @@ InputSlotMorph.prototype.dropDownMenu = function (enableKeyboard) {
                 menu.addLine();
          // } else if (key.indexOf('§_def') === 0) { 
          //     menu.addItem(choices[key].blockInstance(), choices[key]);
-            } else if (key.charAt(key.length - 1) == '{') {
+            } else if (key[key.length - 1] == '{') {
                 // Submenu
                 // 0x25ba = Unicode "BLACK RIGHT-POINTING POINTER"
                 // (not to be confused with "black right-pointing TRIANGLE")
-                menu.addItem(key.substring(0,key.length - 1).
-							 concat(String.fromCharCode(0x25ba)),
+                menu.addItem(key.substring(0,key.length - 1) + '\u25ba',
 							 choices[key]);
                 menuStack.push(menu);
                 menu = new MenuMorph(

byob.js

@@ -299,8 +299,7 @@ CustomBlockDefinition.prototype.dropDownMenuOf = function (inputName) {
             var pair = line.split('='),
 			    unique = pair[0];
 			if (unique == '~' || unique == '}') {
-				unique = unique.concat(gensym.toString());
-				gensym++;
+				unique += gensym++;
 			};
             dict[unique] = isNil(pair[1]) ? unique : pair[1];
         });

morphic.js

@@ -7519,6 +7519,10 @@ MenuMorph.prototype.addLine = function (width) {
     this.items.push([0, width || 1]);
 };
 
+MenuMorph.prototype.addSubmenu = function (key, submenu) {
+	this.addItem(key, key, , , , , , submenu);
+
+
 MenuMorph.prototype.createLabel = function () {
     var text;
     if (this.label !== null) {