attack/damage by trapper and lurker above

Change trappers and lurkers above to remove digestion damage.  They
fold themselves around rather than swallow the victim.  There were
are lot of places that assumed that an engulfer which is an animal
would swallow and digest the victim.  In hindsight, it might have
been simpler to take the M1_ANIMAL flag off of trappers and lurkers
above.

This adds a new digests() predicate for creatures with AT_ENGL+AD_DGST
(purple worm) and also enfolds() for AT_ENGL+AD_WRAP (both 't'-class
critters).

There are several minor fixes mixed in with this.  I didn't record
them as I went along but the two I remember are
1) if poly'd into a holder and holding on to a monster, the '<' and
   '>' commands refursed to work; release the held creature first
   and then treat those commands as normal;
2) throwing a non-weapon while engulfed by an ochre jelly reported
   "the <item> vanishes into the ochre jelly's /currents/".

This needs a lot more testing.  I found and fixed multiple minor
details before my own testing burned out.

doc/fixes3-7-0.txt

@@ -1001,6 +1001,12 @@ blind hero was notified when brass lantern burned out even though it isn't
 	on or off can be determined that way so still gives on/off message
 turn on statushilites automatically if any are defined
 change poison instakill to damage with attribute and max hp loss
+trappers and lurkers above enfold themselves around and crush their victims,
+	not swallow and digest
+attempting to move up or down when poly'd into a holder and holding a monster
+	rejected the move; release the monster instead
+thowing a non-weapon while engulfed by an ochre jelly reported that the item
+	vanished into the jelly's "currents"
 
 
 Fixes to 3.7.0-x Problems that Were Exposed Via git Repository