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.fal

@@ -81,6 +81,7 @@ Housecats have nine lives, kittens only one.
 How long can you tread water?
 Hungry?  There is an abundance of food on the next level.
 I guess you've never hit a mail daemon with the Amulet of Yendor...
+If there's a spot of blood on your hands, why not wash them?
 If you are the shopkeeper, you can take things for free.
 If you ask really nicely, the Wizard will give you the Amulet.
 If you can't learn to do it well, learn to enjoy doing it badly.

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.