Revert misguided attempt at fixing incompatibility between -m and -i switches (better fix coming soon)

Second half of #1752175: #ifdef out references to PyImport_DynLoadFiletab if HAVE_DYNAMIC_LOADING is not defined.

print a slightly more informative message.

sandboxes when bsddb3 tests are run.

object's co_consts tuple; add a test to show that the previous behavior (where
these two constants were "collapsed" into one) causes serious malfunctioning.