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/librustpkg/package_path.rs

@@ -44,8 +44,7 @@ pub fn normalize(p_: RemotePath) -> LocalPath {
 }
 
 pub fn write<W: Writer>(writer: &mut W, string: &str) {
-    let buffer = str::as_bytes_slice(string);
-    writer.write(buffer);
+    writer.write(string.as_bytes());
 }
 
 pub fn hash(data: ~str) -> ~str {