Update to current rust: use the new attributes syntax.

ffi.rs

@@ -7,7 +7,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#[allow(non_camel_case_types)];
+#![allow(non_camel_case_types)]
 
 use std::libc::{c_int, size_t, c_void, c_char};
 

lib.rs

@@ -7,10 +7,10 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#[crate_id = "github.com/mozilla-servo/rust-png#png:0.1"];
-#[crate_type = "lib"];
-#[crate_type = "dylib"];
-#[crate_type = "rlib"];
+#![crate_id = "github.com/mozilla-servo/rust-png#png:0.1"]
+#![crate_type = "lib"]
+#![crate_type = "dylib"]
+#![crate_type = "rlib"]
 
 extern crate std;
 use std::cast;