Fake outs set is now decided by the wallet

This plugs a privacy leak from the wallet to the daemon,
as the daemon could previously see what input is included
as a transaction input, which the daemon hadn't previously
supplied. Now, the wallet requests a particular set of
outputs, including the real one.

This can result in transactions that can't be accepted if
the wallet happens to select too many outputs with non standard
unlock times. The daemon could know this and select another
output, but the wallet is blind to it. It's currently very
unlikely since I don't think anything uses non default
unlock times. The wallet requests more outputs than necessary
so it can use spares if any of the returns outputs are still
locked. If there are not enough spares to reach the desired
mixin, the transaction will fail.

src/cryptonote_core/blockchain.h

@@ -439,6 +439,21 @@ namespace cryptonote
      */
     bool get_random_outs_for_amounts(const COMMAND_RPC_GET_RANDOM_OUTPUTS_FOR_AMOUNTS::request& req, COMMAND_RPC_GET_RANDOM_OUTPUTS_FOR_AMOUNTS::response& res) const;
 
+    /**
+     * @brief gets specific outputs to mix with
+     *
+     * This function takes an RPC request for outputs to mix with
+     * and creates an RPC response with the resultant output indices.
+     *
+     * Outputs to mix with are specified in the request.
+     *
+     * @param req the outputs to return
+     * @param res return-by-reference the resultant output indices and keys
+     *
+     * @return true
+     */
+    bool get_outs(const COMMAND_RPC_GET_OUTPUTS::request& req, COMMAND_RPC_GET_OUTPUTS::response& res) const;
+
     /**
      * @brief gets the global indices for outputs from a given transaction
      *