Disable Chicken target language

Clean up to disable target languages that have been neglected/not functional.
Target language be fully deleted in SWIG 4.1 unless a new maintainer brings
it up to an acceptable status (experimental or supported).

Issue #1447

Doc/Manual/SWIG.html

@@ -119,7 +119,6 @@ for example, <tt>swig -ruby -help</tt> for Ruby.
 <div class="shell"><pre>
 Supported Target Language Options
      -allegrocl      - Generate ALLEGROCL wrappers
-     -chicken        - Generate CHICKEN wrappers
      -cffi           - Generate CFFI wrappers
      -csharp         - Generate C# wrappers
      -d              - Generate D wrappers