probing while swallowed (trunk only)

Reported recently by <Someone>:  probing feedback while engulfed
shouldn't claim that the monster is not carrying anything when the hero
is inside of it.  The simple case where it's not carrying anything else
was a trivial one line change; handling inventory plus hero was trickier
and I wouldn't have bothered if I'd realized what it was going to take.
But it's done now; trivial case
        The purple worm is not carrying anything besides you.
and harder case
        The purple worm's possessions:
        Weapons
        a - an uncursed dagger
        Swallowed Creature
        > - human archeologist called wizard

include/extern.h

@@ -1614,6 +1614,7 @@ E void NDECL(set_playmode);
 
 /* ### pager.c ### */
 
+E char *FDECL(self_lookat, (char *));
 E int NDECL(dowhatis);
 E int NDECL(doquickwhatis);
 E int NDECL(doidtrap);