Update region inference for traits so that a method with

explicit self doesn't incorrectly cause the entire trait to
be tagged as being region-parameterized.

Fixes #5224.

src/libsyntax/print/pprust.rs

@@ -30,7 +30,6 @@ use print::pprust;
 use core::char;
 use core::dvec::DVec;
 use core::io;
-use core::option;
 use core::str;
 use core::u64;
 use core::vec;