Fix monster trapped state being wrong

When cloning a monster, clear the clone trapped and hiding states.
When splitting a monster (eg. a black pudding), the clone could
be placed on a trap, so do mintrap.
When removing a monster from the map, clear the trapped state.

src/mhitm.c

@@ -419,7 +419,8 @@ register struct monst *magr, *mdef;
                                  || objects[otmp->otyp].oc_material == METAL))
                     && mdef->mhp > 1
                     && !mdef->mcan) {
-                    if (clone_mon(mdef, 0, 0)) {
+                    struct monst *mclone;
+                    if ((mclone = clone_mon(mdef, 0, 0)) != 0) {
                         if (vis && canspotmon(mdef)) {
                             char buf[BUFSZ];
 
@@ -427,6 +428,7 @@ register struct monst *magr, *mdef;
                             pline("%s divides as %s hits it!", buf,
                                   mon_nam(magr));
                         }
+                        mintrap(mclone);
                     }
                 }
             } else