Digestion attack can grant hero intrinsics

Monster purple worms can now gain intrinsics from swallowing foes whole,
so maybe the hero should be able to do so too.  Intrinsics aren't
granted immediately upon swallowing (that would probably have been
easier), but only once a corpse is created and then entirely digested.

I'm not sure if this is too powerful and was being avoided deliberately
for that reason, since it includes potential level gain from wraith
corpses in addition to other intrinsics.  That's consistent with monster
purple worms but may be a bit too much in the hands of the hero, though
it is limited by needing the corpse creation roll to succeed.

include/decl.h

@@ -1257,6 +1257,7 @@ struct instance_globals {
     /* uhitm.c */
     boolean override_confirmation; /* Used to flag attacks caused by
                                     * Stormbringer's maliciousness. */
+    short corpsenm_digested; /* monster type being digested, set by gulpum */
 
     /* vision.c */
     seenV **viz_array; /* used in cansee() and couldsee() macros */

include/extern.h

@@ -775,6 +775,7 @@ extern void set_tin_variety(struct obj *, int);
 extern int tin_variety_txt(char *, int *);
 extern void tin_details(struct obj *, int, char *);
 extern boolean Popeye(int);
+extern int Finish_digestion(void);
 
 /* ### end.c ### */