message: [pdsl_model] Add ExecutionEnv::return fn
diff: @@ -24,4 +24,11 @@ impl<State> ExecutionEnv<State> {
  pub fn caller(&self) -> Address {
  ContractEnv::caller()
  }
  +
  + pub fn r#return<T>(&self, val: T) -> !
  + where
  + T: parity_codec::Encode,
  + {
  + ContractEnv::return_(&val.encode()[..])
  + }
  }
  