rollup merge of #20081: tomjakubowski/issue-19646

Encode foreign item attributes and stability levels and visit foreign
items in the stability visitor.

cc @Gankro

diff --cc src/librustc/middle/stability.rs
index c4a5fd2f14a3ccd739779dcc83ec1cb82bbcb516,3e874f46a338c5ca9971f75834c0468c5fe59298..9d032df67dc8bcd461a81afe726c291c0f03cfeb
--- 1/src/librustc/middle/stability.rs
--- 2/src/librustc/middle/stability.rs
+++ b/src/librustc/middle/stability.rs
@@@ -126,9 -109,12 +126,13 @@@ impl<'v> Visitor<'v> for Annotator 
      }
  
      fn visit_struct_field(&mut self, s: &StructField) {
 -        self.annotate(s.node.id, &s.node.attrs, |v| visit::walk_struct_field(v, s));
 +        self.annotate(s.node.id, true, &s.node.attrs,
 +                      |v| visit::walk_struct_field(v, s));
      }
+ 
+     fn visit_foreign_item(&mut self, i: &ast::ForeignItem) {
+         self.annotate(i.id, &i.attrs, |_| {});
+     }
  }
  
  impl Index {