Fix contract::get_datastream() accessor

libraries/eosiolib/contracts/eosio/contract.hpp

@@ -30,7 +30,7 @@ class contract {
        * Construct a new contract given the contract name
        *
        * @param self - The name of the account this contract is deployed on
-       * @param first_receiver - The account the incoming action was first received at. 
+       * @param first_receiver - The account the incoming action was first received at.
        * @param ds - The datastream used
        */
       contract( name self, name first_receiver, datastream<const char*> ds ):_self(self),_first_receiver(first_receiver),_ds(ds) {}
@@ -52,7 +52,7 @@ class contract {
       inline name get_code()const { return _first_receiver; }
 
       /**
-       * The account the incoming action was first received at. 
+       * The account the incoming action was first received at.
        *
        * @return name - The first_receiver name of the action this contract is processing.
        */
@@ -63,7 +63,14 @@ class contract {
        *
        * @return datastream<const char*> - The datastream for this contract
        */
-      inline datastream<const char*> get_datastream()const { return _ds; }
+      inline datastream<const char*>& get_datastream() { return _ds; }
+
+      /**
+       * Get the datastream for this contract
+       *
+       * @return datastream<const char*> - The datastream for this contract
+       */
+      inline const datastream<const char*>& get_datastream()const { return _ds; }
 
    protected:
       /**
@@ -72,7 +79,7 @@ class contract {
       name _self;
 
       /**
-       * The account the incoming action was first received at. 
+       * The account the incoming action was first received at.
        */
       name _first_receiver;