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/asm.rs

@@ -21,8 +21,6 @@ use ext::base::*;
 use parse;
 use parse::token;
 
-use core::vec;
-
 enum State {
     Asm,
     Outputs,