chore: name the event callback used by ngClick and friends

This maskes looking at stack traces easier.

Since we generate the callbacks for each event type at runtime and we can't
set function's name because it's read-only, we have to use a generic name.

src/ng/directive/ngEventDirs.js

@@ -45,7 +45,7 @@ forEach(
       return {
         compile: function($element, attr) {
           var fn = $parse(attr[directiveName]);
-          return function(scope, element, attr) {
+          return function ngEventHandler(scope, element) {
             element.on(lowercase(name), function(event) {
               scope.$apply(function() {
                 fn(scope, {$event:event});