Add MyLocalStruct

This clearly shows that implementors local to the trait-defining crate
get linked to, while implementors that are downstream do not get links.

Author: camelid

crate_a/src/lib.rs

@@ -1 +1,5 @@
 pub trait MyTrait {}
+
+pub struct MyLocalStruct;
+
+impl MyTrait for MyLocalStruct {}