polymorphing worn items (trunk only)

From a bug report.  That's hard to fix in the general case because armor
and tools might not fit back into the same equipment slot, but most other
types of worn items can be re-worn after being transformed.  This makes
any transformed worn item stay worn if it is wearable in the same slot.

doc/fixes35.0

@@ -172,6 +172,7 @@ shops now claim ownership of items created by using an unpaid horn of plenty
 shopkeepers shouldn't refer to non-male character as "cad"
 tweak levitation timeout if trap is being triggered on same turn it is to end
 if Rider corpse revival fails, usually try again later instead of rotting away
+worn item transformed by polymorph remains worn if feasible
 
 
 Platform- and/or Interface-Specific Fixes