more care around generated names, fixes #60 #82 and #97

test/codegen/expect/sunflower/dom.js

 var dom;
 (function(exports) {
   'use strict';
   class JsName extends core.Object {
-    JsName(opt$) {
-      let name = opt$ && 'name' in opt$ ? opt$.name : null;
+    JsName(opts) {
+      let name = opts && 'name' in opts ? opts.name : null;
       this.name = name;
     }
   }
   class Overload extends core.Object {
     Overload() {
     }
   }
   let overload = new Overload();
   class Event extends core.Object {
   }
@@ skipping 15 matching lines @@
   }
   // Exports:
   exports.JsName = JsName;
   exports.Overload = Overload;
   exports.overload = overload;
   exports.Event = Event;
   exports.RenderingContext = RenderingContext;
   exports.CanvasDrawingStyles = CanvasDrawingStyles;
   exports.CanvasPathMethods = CanvasPathMethods;
 })(dom || (dom = window));