Fixed option to disable all CSS Async features on mobile devices.
Fixed incompatibility with WPtouch plugin.
Update function wp_is_mobile() on lazy load images to really disabled this feature on mobile devices.

git-svn-id: https://plugins.svn.wordpress.org/speed-booster-pack/trunk@946769 b8457f37-d9ea-0310-8a92-e5e31aec5664