itemized billing vs persistent inventory, round II

Reported by entrez:  buying an unpaid item using itemized billing used
to result in the price information for unpaid items disappearing when
they get shown by perm_invent.  (Their status as unpaid didn't change;
persistent inventory just got redrawn without cost information.)  The
fix for that didn't handle buying a used-up item.  There's no invent
update for the gone-item item but there is one for moving gold out of
hero's inventory to add to shopkeeper's inventory.  The vanishing
price phenomenon applied to that situation too.

I can't think of any situation where persistent inventory would want
to hide unpaid status and/or cost, so always prevent those from being
excluded during perm_invent update.

doc/fixes3-7-0.txt

@@ -1250,6 +1250,10 @@ after the fix for zombie reviving near hero (which now interrupts hero's
 	it revived on the same turn that eating the corpse would finish
 a wizard's starting equipment was supposed to include a random spellbook of
 	spell level 1 through 3 but it was being foced to be level 1
+earlier fix for prices of unpaid objects going away in persistent inventory
+	display when hero bought something during itemized billing didn't work
+	if paying for a used-up shop item--prices of any unpaid items vanished
+	when inventory got updated to reflect transfer of hero's gold to shk
 
 curses: 'msg_window' option wasn't functional for curses unless the binary
 	also included tty support