Migrate rpc-servers, serializer, service and sr-io to the 2018 edition (#1732)

substrate/core/primitives/src/lib.rs

@@ -21,6 +21,8 @@
 #![cfg_attr(not(feature = "std"), no_std)]
 #![cfg_attr(not(feature = "std"), feature(alloc))]
 
+/// Creates a vector of given pairs and calls `collect` on the iterator from it.
+/// Can be used to create a `HashMap`.
 #[macro_export]
 macro_rules! map {
 	($( $name:expr => $value:expr ),*) => (