fix($compile): don't check attr.specified on non-ie7

the specified attribute is depricated and creates warnings in Firefox

Closes #3231
Closes #2160

src/ng/compile.js

@@ -556,7 +556,7 @@ function $CompileProvider($provide) {
             var index;
 
             attr = nAttrs[j];
-            if (attr.specified) {
+            if (!msie || msie >= 8 || attr.specified) {
               name = attr.name;
               // support ngAttr attribute binding
               ngAttrName = directiveNormalize(name);