Add a faster code path for calling builtin methods

Add a faster code path for calling builtin methods

Builtin methods usually don't need a Context of their own,
so we can fully avoid the overhead of creating and destroying
it.

Implemented the support for making builtin methods context less
and verified it with some of the methods in String.prototype.

Change-Id: I187b46ba684183b4fba49ae70e3139d32ef585e0
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>