display former possessions of dead monster

display former possessions of dead monster

Reported directly to devteam by a hardfought player and also by
entrez.  The recent mon_leaving_level() change resulted in objects
dropped by a dying monster not being displayed immediately.

It justed needed the relobj(mon, 0, FALSE) to relobj(mon, 1, FALSE)
change in m_detach() but this does some related cleanup in
mon_leaving_level()'s callers.  wormgone() takes a long worm off the
map but leaves its stale coordinates set because some code relied on
that.  This takes away the need for that but still doesn't actually
clear them.

This adds redundant 'return' statements at the end of a few void
functions that are longer than fits within a typical screen display.
They make searching for the end of the current routine in an editor
or pager easier without resorting to regular expressions and can
also be used to search for the beginning if/when preceding routine
ends in 'return' too.