clearing no_charge bit for containers

[I can't get access to my mail at present, but `cvs update' shows
that there aren't any patch notification messages pending for me.]

     Extend a pre-3.4.3 fix--for objects picked up in an untended shop--
to container contents.  Without it, dropping a bag or box in a tended shop
and declining to sell it, then picking it back up after the shop has become
untended (shk killed or evicted) would leave the contents with no_charge
set.  After that it could be sold in another tended shop, picked back up
for free, then kept or sold a second time.  (Picking it back up in the
tended shop would clear the bit; afterwards it behaved normally.  And it's
not something prone to abuse; if you can make a tended shop become untended
you really don't need to sell stuff twice.  But it'd be noticeably wrong if
anyone ever stumbled across it.)

doc/fixes34.4

@@ -107,6 +107,8 @@ fix various places that "finally finished" could be displayed after the hero
 fix some cases where movement was disallowed but the hero was still conscious
 after destroying drawbridge, hero could appear to be in the wall
 sometimes shop items which hero is forced to buy could be sold back twice
+non-empty container dropped but not sold in a tended shop and then picked up
+	after that shop became untended could be sold twice in another shop
 vision was not updated when polymorphing a statue into a boulder
 `I u' when carrying single unpaid item listed its cost twice
 armor which auto-curses when worn by hero should do same if worn by monster