Eyes plus stinking cloud

stinking clouds extend their timers, causing the "ttl == 0" check in
visible_region_at to be inappropriate; technically it was never quite
right, since the ttl is set to 0 one turn before removal is considered. But
with the Eyes on, this caused a visible change in the region although the
region still existed.  Introduced a new -2L value to designate that the
region is being removed (-1L means it's permanent), which is what
visible_region_at was really trying to test.

doc/fixes34.4

@@ -255,6 +255,8 @@ hero is not subject to light-based blindness while fainted from hunger
 engraving while underwater should use surface() which handles that case
 prevent obj_is_local panic during bones creation when splatter_burning_oil()
 	from a thrown potion of oil kills the hero
+fix region timeout detection, caused strange display of stinking cloud
+	while wearing the Eyes of the Overworld
 
 
 Platform- and/or Interface-Specific Fixes

src/region.c

@@ -339,6 +339,7 @@ NhRegion *reg;
 	return;
 
     /* Update screen if necessary */
+    reg->ttl = -2L;			/* for visible_region_at */
     if (reg->visible)
 	for (x = reg->bounding_box.lx; x <= reg->bounding_box.hx; x++)
 	    for (y = reg->bounding_box.ly; y <= reg->bounding_box.hy; y++)
@@ -600,7 +601,7 @@ xchar x, y;
 
     for (i = 0; i < n_regions; i++)
 	if (inside_region(regions[i], x, y) && regions[i]->visible &&
-		regions[i]->ttl != 0L)
+		regions[i]->ttl != -2L)
 	    return regions[i];
     return (NhRegion *) 0;
 }