Refactor : pushFrame is replaced with passing argument to evaluation con...

I did performance tests and apparently the biggest load is in HashMap.putAll (from pushStackFrame). I'm trying to understand how to workaround this place. 
But first of all, I would like to refactor push/pop relations to see how much it is used. It is a good practice to have matching push and pop methods (and actually for safety reasons, put pop into finally block).

Please review the change and comment it if you feel uncomfortable with it.