fix message when monster's two-handed weapon welds

K3610 reported to devteam:
When you see a monster wield a cursed two-handed weapon,
the weapon "welds itself to the foo's hand" instead of its "hands."

Observed on hill orcs wielding a cursed two-handed sword.

doc/fixes3-7-0.txt

@@ -915,6 +915,8 @@ if player gave a subset count when removing an item from a container, then got
 	the pickup_burden prompt and declined to continue, the item remained
 	split rather be recombined, making it possible to create multiple
 	stacks of gold inside a container
+two-handed weapon message stated "welded to monsters hand" instead of
+	"welded to monsters hands"
 
 
 Fixes to 3.7.0-x Problems that Were Exposed Via git Repository

src/weapon.c

@@ -836,9 +836,13 @@ mon_wield_item(struct monst *mon)
             newly_welded = mwelded(obj);
             obj->owornmask &= ~W_WEP;
             if (newly_welded) {
+                const char *mon_hand = mbodypart(mon, HAND);
+
+                if (bimanual(obj))
+                    mon_hand = makeplural(mon_hand);
                 pline("%s %s to %s %s!", Tobjnam(obj, "weld"),
                       is_plural(obj) ? "themselves" : "itself",
-                      s_suffix(mon_nam(mon)), mbodypart(mon, HAND));
+                      s_suffix(mon_nam(mon)), mon_hand);
                 obj->bknown = 1;
             }
         }