Enhance decl storage (#777)

* enhance macro decl_storage()

* update the state root hash

* fix one comment

substrate/srml/support/src/lib.rs

@@ -29,6 +29,8 @@ extern crate serde;
 
 extern crate sr_std as rstd;
 extern crate sr_io as runtime_io;
+#[cfg(feature = "std")]
+pub extern crate sr_primitives as runtime_primitives;
 extern crate substrate_metadata;
 
 extern crate mashup;