std: unify the str -> [u8] functions as 3 methods: .as_bytes() and .as_bytes_with_null[_consume]().

The first acts on &str and is not nul-terminated, the last two act on strings
that are always null terminated (&'static str, ~str and @str).

src/libsyntax/ext/base.rs

@@ -22,7 +22,6 @@ use parse::token;
 use parse::token::{ident_to_str, intern, str_to_ident};
 
 use core::hashmap::HashMap;
-use core::vec;
 
 // new-style macro! tt code:
 //