lint: add lint for use of a ~[T].

This is useless at the moment (since pretty much every crate uses
`~[]`), but should help avoid regressions once completely removed from a
crate.

src/test/compile-fail/lint-unused-mut-variables.rs

@@ -13,6 +13,7 @@
 #[allow(dead_assignment)];
 #[allow(unused_variable)];
 #[allow(dead_code)];
+#[allow(deprecated_owned_vector)];
 #[deny(unused_mut)];
 
 fn main() {