refactor map macro for more general use

core/primitives/src/lib.rs

@@ -26,9 +26,9 @@
 /// Can be used to create a `HashMap`.
 #[macro_export]
 macro_rules! map {
-	($( $name:expr => $value:expr ),*) => (
+    ($( $name:expr => $value:expr ),* $(,)? ) => (
 		vec![ $( ( $name, $value ) ),* ].into_iter().collect()
-	)
+    );
 }
 
 use rstd::prelude::*;