"Placing monster over another?" warning was triggered for vault guard
by an earlier change which made m_detach() stop removing monsters at
<0,*> from level.monsters[][]. So one guard would replace another at
<0,0> for however many guards were created, and memory for all but
the last one would be lost.
This involved a lot of flailing about and the patch includes various
things would could have been discarded. One or two extended monster
sanity checks are included, plus a couple of debugpline()'s for
tracking guard movement.
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