buglist - full level triggers impossible() from migrating mons

<email deleted> wrote:
> If more monsters fall through a trap door than can fit on the
> level below, when you go down the stairs, you get the following
> message:
>  "Program in disorder - perhaps you'd better #quit.
>  rloc(): couldn't relocate monster"
> This message seems to appear once for every monster-too-many that
> fell through the hole. I originally found this while
> intentionally completely filling a level with black puddings
> (there was a trap door I didn't know about). I also confirmed it
> in a wiz-mode test using gremlins and water.

[confirmed: moveloop -> deferred_goto -> goto_level ->
 losedogs -> mon_arrive -> rloc -> impossible]

This patch:
- causes rloc() to return TRUE if successful,
  or FALSE if it wasn't.
- adds code to mon_arrive() in dog.c to deal with
  the failed rloc()
- allows the x,y parameters to mkcorpstat() to
  be 0,0 in order to trigger random placement of the
  corpse on the level
- if you define DEBUG_MIGRATING_MONS when you build cmd.c
  then you'll have a debug-mode command #migratemons to
  store the number of random monsters that you specify
  on the migrating monsters chain.

src/priest.c

@@ -186,7 +186,7 @@ boolean sanctum;   /* is it the seat of the high priest? */
 	int cnt;
 
 	if(MON_AT(sx+1, sy))
-		rloc(m_at(sx+1, sy)); /* insurance */
+		(void) rloc(m_at(sx+1, sy), FALSE); /* insurance */
 
 	priest = makemon(&mons[sanctum ? PM_HIGH_PRIEST : PM_ALIGNED_PRIEST],
 			 sx + 1, sy, NO_MM_FLAGS);
@@ -532,7 +532,7 @@ boolean peaceful;
 	if (ptr != &mons[PM_ALIGNED_PRIEST] && ptr != &mons[PM_ANGEL])
 		return((struct monst *)0);
 	
-	if (MON_AT(x, y)) rloc(m_at(x, y));	/* insurance */
+	if (MON_AT(x, y)) (void) rloc(m_at(x, y), FALSE);	/* insurance */
 
 	if (!(roamer = makemon(ptr, x, y, NO_MM_FLAGS)))
 		return((struct monst *)0);