Get rid of Get/SetHiddenValue in the v8 API

It was only used to mark an object as something to be used as a binding.
Simply use one of the free bits in QV4::Managed for that.

Also changed a bit more code over from v8 to v4.

Change-Id: I6e787e611041e058fe109df1d7a13598655f8eba
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>
Add symbolification for MacOS.

Change-Id: I95fc25afef56dad7c51f417959728397e63a8dc1
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>