Update release notes to reflect z_sendmany changes

doc/release-notes.md

@@ -4,3 +4,31 @@ release-notes at release time)
 Notable changes
 ===============
 
+Wallet
+------
+
+`z_sendmany`
+------------
+
+- The `z_sendmany` RPC call no longer permits Sprout recipients in the 
+  list of recipient addresses. Transactions spending Sprout funds will
+  still result in change being sent back into the Sprout pool, but no
+  other `Sprout->Sprout` transactions will be constructed by the Zcashd
+  wallet. 
+
+- The restriction that prohibited `Sprout->Sapling` transactions has been 
+  lifted; however, since such transactions reveal the amount crossing 
+  pool boundaries, they must be explicitly enabled via a parameter to
+  the `z_sendmany` call.
+
+- A new boolean parameter, `allowRevealedAmounts`, has been added to the
+  list of arguments accepted by `z_sendmany`. This parameter defaults to
+  `false` and is only required when the transaction being constructed 
+  would reveal transaction amounts as a consequence of ZEC value crossing
+  shielded pool boundaries via the turnstile.
+
+- Since Sprout outputs are no longer created (with the exception of change)
+  `z_sendmany` no longer generates payment disclosures (which were only 
+  available for Sprout outputs) when the `-paymentdisclosure` experimental
+  feature flag is set.
+