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/muse.c

@@ -592,7 +592,7 @@ mon_tele:
 		    return 2;
 		}
 		if (oseen && how) makeknown(how);
-		rloc(mtmp);
+		(void) rloc(mtmp, FALSE);
 		return 2;
 	case MUSE_WAN_TELEPORTATION:
 		zap_oseen = oseen;
@@ -1148,7 +1148,7 @@ register struct obj *otmp;
 			    mtmp->msleeping = 0;
 			    if(mtmp->m_ap_type) seemimic(mtmp);
 			} else if (!tele_restrict(mtmp))
-			    rloc(mtmp);
+			    (void) rloc(mtmp, FALSE);
 		}
 		break;
 	case WAN_CANCELLATION: