Implement "&<pat> everywhere"

The original proposal allows reference patterns
with "compatible" mutability, however it's not clear
what that means so for now we require an exact match.

I don't know the type system code well, so if something
seems to not make sense it's probably because I made a
mistake

compiler/rustc_span/src/symbol.rs

@@ -380,6 +380,7 @@ symbols! {
         alu32,
         always,
         and,
+        and_pat_everywhere,
         and_then,
         anon,
         anon_adt,