fix pull request #469 - multiple '$' invent slots

Assigning a partial stack of gold to quiver (Qnn$) resulted in
an extra '$' slot in inventory, one for the unquivered part and
another for the quivered part.

Throwing a non-quivered partial stack of gold at self (tnn$.)
also resulted in an extra '$' slot after throwing at self was
rejected.

For the first case, reject the quiver-subset-of-gold attempt.
For both cases, recombine the two stacks back to original amount.

Fixes #469

src/wield.c

@@ -499,6 +499,11 @@ dowieldquiver(void)
         if (uquiver && uquiver->o_id == g.context.objsplit.parent_oid) {
             unsplitobj(newquiver);
             goto already_quivered;
+        } else if (newquiver->oclass == COIN_CLASS) {
+            /* don't allow splitting a stack of coins into quiver */
+            You("can't ready only part of your gold.");
+            unsplitobj(newquiver);
+            return 0;
         }
         finish_splitting = TRUE;
     } else if (newquiver == uquiver) {