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/mkobj.c

@@ -894,7 +894,11 @@ boolean init;
 
 	if (objtype != CORPSE && objtype != STATUE)
 	    impossible("making corpstat type %d", objtype);
-	otmp = mksobj_at(objtype, x, y, init, FALSE);
+	if (x == 0 && y == 0) {		/* special case - random placement */
+		otmp = mksobj(objtype, init, FALSE);
+		if (otmp) rloco(otmp);
+	} else
+		otmp = mksobj_at(objtype, x, y, init, FALSE);
 	if (otmp) {
 	    if (mtmp) {
 		struct obj *otmp2;