(osx) deprecate OSX platform in documentation (#1117)

* add note that OSX platform is now deprecated

* show "(deprecated)" in TOC title

* use "future" instead of "new"

Author: Chris Brody

www/docs/en/dev/guide/platforms/osx/index.md

@@ -18,11 +18,13 @@ license: >
     under the License.
 
 title: OS X Platform Guide
-toc_title: OS X
+toc_title: OS X (deprecated)
 ---
 
 # OS X Platform Guide
 
+**NOTICE:** The OS X platform is now deprecated and may be removed from a future version of Cordova.
+
 This guide shows how to set up your SDK development environment to
 deploy Cordova apps for OS X computers. See the
 following for more detailed platform-specific information: