Deprecate fourcc.

src/libfourcc/lib.rs

@@ -40,7 +40,8 @@ fn main() {
 */
 
 #![crate_name = "fourcc"]
-#![experimental]
+#![deprecated = "This is now a cargo package located at: \
+                 https://github.com/rust-lang/fourcc"]
 #![crate_type = "rlib"]
 #![crate_type = "dylib"]
 #![license = "MIT/ASL2"]