more sortloot - picking up cockatrice corpses

Yesterday's sortloot() overhaul didn't include some cockatrice corpse
handling for pickup.  If there's an object class filter in place and
pickup has been told to care about cockatrice corpses, have sortloot()
include them in the loot array even if food class isn't accepted by
the filter.  In the pre-sortloot days, and in 3.6.[01] which didn't
attempt to deliver a filtered subset of loot, the check for such
corpses was done before pickup checks the filter.  They need to be in
the loot array to retain the same behavior.

include/hack.h

@@ -376,6 +376,7 @@ enum explosion_types {
 #define SORTLOOT_PACK   0x01
 #define SORTLOOT_INVLET 0x02
 #define SORTLOOT_LOOT   0x04
+#define SORTLOOT_PETRIFY 0x20 /* override filter func for c-trice corpses */
 
 /* flags for xkilled() [note: meaning of first bit used to be reversed,
    1 to give message and 0 to suppress] */