Add a new wand, the wand of stasis

A wand of stasis prevents teleportation (even in some cases where
it would normally not be prevented, e.g. the hero teleporting a
monster, or covetous monsters teleporting). This is intended to
provide an alternative tactic against covetous monsters (and their
AI has been adjusted to handle being under a stasis effect), but
might also be useful in other situations. It does not prevent
teleportation of objects, only the hero / monsters, and does not
at present prevent level teleportation (although I'm not sure about
this and it might well change in the future).

This breaks save compatibility, but is being pushed together with
other save-breaking changes to avoid the need for multiple bumps to
EDITLEVEL.

doc/fixes3-7-0.txt

@@ -2907,6 +2907,7 @@ the game now automatically tracks which sell prices and buy prices you have
         seen for each type of item; these are visible in the discoveries list,
         and can also be shown elsewhere using the new 'price_quotes' option
 new shields: shield of shock resistance, shield of drain resistance
+new wand: wand of stasis
 
 
 Platform- and/or Interface-Specific New Features