Deprecate cocoa, cocoa-foundation and io-surface and link to objc2 crates instead (#731)

* Deprecate cocoa-foundation

* Deprecate cocoa

* Deprecate io-surface

cocoa-foundation/src/base.rs

@@ -6,6 +6,7 @@
 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
+#![deprecated = "use the objc2 crate instead"]
 
 use objc::runtime;
 

cocoa-foundation/src/foundation.rs

@@ -6,7 +6,7 @@
 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
-
+#![deprecated = "use the objc2-foundation crate instead"]
 #![allow(non_upper_case_globals)]
 
 use crate::base::{id, nil, BOOL, NO, SEL};

cocoa-foundation/src/lib.rs

@@ -7,7 +7,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![allow(non_snake_case)]
+//! This crate has been deprecated in favour of the `objc2-foundation` crate.
+#![allow(non_snake_case, deprecated)]
 
 pub mod base;
 pub mod foundation;

cocoa-foundation/tests/foundation.rs

@@ -1,3 +1,5 @@
+#![allow(deprecated)]
+
 #[cfg(test)]
 mod foundation {
     mod nsstring {