More region fixes. The region restore code wasn't updating monster
ID numbers for bones data, so monsters already inside stinking clouds
might or might not be affected by them depending on arbitrary mon->mid
assignments across the old and new games.
This also flags stinking clouds in a way that lets the game keep
track of whether they were created by the player, and clears that state
for bones data so that the current player doesn't get credit or blame
for clouds left by the former one. File compatibility with 3.4.0 is
retained; if/when that eventually changes, this code can be simplified.
Testing with current development code has been limited but seems
to be working correctly; testing with actual 3.4.0 files has not been
attempted.
