non-digest engulfing

Be more consistent with the engulf attack feedback by creatures who
fold themselves around the victim (trapper, lurker above) rather than
swallow or directly engulf.

Replace an instance of a non-literal format string and the warnings
manipulation it needed with a literal one.

src/mhitu.c

@@ -1203,6 +1203,7 @@ gulpmu(struct monst *mtmp, struct attack *mattk)
         } else {
             urgent_pline("%s %s!", Monnam(mtmp),
                          digests(mtmp->data) ? "swallows you whole"
+                         : enfolds(mtmp->data) ? "folds itself around you"
                            : "engulfs you");
         }
         stop_occupation();
@@ -1210,7 +1211,7 @@ gulpmu(struct monst *mtmp, struct attack *mattk)
 
         if (u.utrap) {
             You("are released from the %s!",
-                u.utraptype == TT_WEB ? "web" : "trap");
+                (u.utraptype == TT_WEB) ? "web" : "trap");
             reset_utrap(FALSE);
         }