Q10: make_call_frame()
Q12: scheme_apply()

and bugfix + doctests in Frame.lookup().
Scheme Tests 1.1.4 passing
Q13: do_if_form()
Q14: do_and_form(), do_or_form()
Q15: do_cond_form()
Move (exit) to include more tests

We don't have the let form implemented yet, so we can't test that.
Q16: do_let_form()