Explicitly declare decl_storage! getters as functions (#3870)

* parse decl_storage getters with fn keyword

* test for get in decl_storage

* update all decl_storage! getters

* bump version

* adjust missed doc line

substrate/srml/timestamp/src/lib.rs

@@ -244,7 +244,7 @@ decl_module! {
 decl_storage! {
 	trait Store for Module<T: Trait> as Timestamp {
 		/// Current time for the current block.
-		pub Now get(now) build(|_| 0.into()): T::Moment;
+		pub Now get(fn now) build(|_| 0.into()): T::Moment;
 
 		/// Did the timestamp get updated in this block?
 		DidUpdate: bool;