added morrie's law; renamed _match11 to _match_f_plus_1, etc.
replaced ``replace_mul_f2`` with ``replace_mul_f2g``; added ``_artifact1``
``_replace_mult_morrie`` also for ``cosh``; fixed bug
replace_mul_fpowf2 improved
replaced ``to_tan`` with ``with_tan``; added cases to ``_match_div_rewrite``;
fixed bug in ``replace_mul_fpowf2``; added tests