Build: Workaround strict mode violations caused by UglifyJS

This commit increases the gzipped size by 90 bytes so a better solution
is needed but, at the same time, it disables the very optimizations
that are causing strict mode violations in Firefox 45, Safari 9 & IE 10.

Refs 7608437
Refs mishoo/UglifyJS#1052

Author: mgol

Gruntfile.js

@@ -186,6 +186,7 @@ module.exports = function( grunt ) {
 					banner: "/*! jQuery v<%= pkg.version %> | " +
 						"(c) jQuery Foundation | jquery.org/license */",
 					compress: {
+						"if_return": false,
 						"hoist_funs": false,
 						loops: false,
 						unused: false