work towards compile_fake_exp_val

cheating on the claim that evaluate in an equivalent (as an association
list) environment gives an equivalent (syneq after v_to_Cv) result.
more compile_fake_exp_val
more compile_fake_exp_val
more compile_fake_exp_val
finish compile_fake_exp_val

excepting a cheat for the lemma about swapping in an equivalent source
language environment. not sure how easy that will be to prove, but
hoping it's true. also hoping this statement of compile_fake_exp_val is
good enough for compile_dec.