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/log_syntax.rs

@@ -18,7 +18,6 @@ use print;
 use parse::token::{get_ident_interner};
 
 use core::io;
-use core::vec;
 
 pub fn expand_syntax_ext(cx: @ExtCtxt,
                          sp: codemap::span,