Make psh/pul error out if no registers given While the generated object code was technically correct for bare pshs, puls, pshu, and pulu, it was not helpful. Throw a bad operand error if no registers are given as an operand to such instructions. Thanks to Erik G <erik@6809.org> for reporting the problem.

See the file GPL3 for a copy of the GNU General Public License, version 3,
under which the majority of this distribution is licensed.

Some specific source files, including many of those in the lwcc subdirectory
are licensed differently. See each individual file for specific details.