Add rumors related to sink, hand-washing changes

These can hint at some of the changes that make it possible to dip
potions in sinks to potentially get a hint to their identity, and wash
your hands in sinks, pools, and fountains.  I also mentioned rings in
the potion/sink rumor since there didn't seem to be a rumor about the
sink ring ID mechanic already (though there may be one in coded language
that my grepping didn't catch).  The false rumor about hand-washing felt
to me like a good spot for a Macbeth reference.

dat/rumors.tru

@@ -89,6 +89,7 @@ If you need a wand of digging, kindly ask the minotaur.
 If you want to hit, use a dagger.
 If you want to rob a shop, train your dog.
 If you're lost, try buying a map next time you're in a shop.
+If your hands are greasy, why not wash them?
 Inside a shop you better take a look at the price tags before buying anything.
 It is bad manners to use a wand in a shop.
 It is dangerous to visit a graveyard at midnight.
@@ -367,5 +368,6 @@ You should certainly learn about quantum mechanics.
 You won't always get a second chance, even with life saving.
 You're going into the morgue at midnight???
 Your dog knows what to eat; maybe you should take lessons.
+Your game may go down the drain if you have extra potions or rings.
 Zap yourself and see what happens...
 Zapping a wand of undead turning might bring your dog back to life.