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/Preprocessor.html

@@ -111,7 +111,6 @@ SWIG_VERSION                    Hexadecimal (binary-coded decimal) number contai
 
 SWIGALLEGROCL                   Defined when using Allegro CL
 SWIGCFFI                        Defined when using CFFI
-SWIGCHICKEN                     Defined when using CHICKEN
 SWIGCSHARP                      Defined when using C#
 SWIGGUILE                       Defined when using Guile
 SWIGJAVA                        Defined when using Java

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

Doc/Manual/Sections.html

@@ -42,7 +42,6 @@ Last update : SWIG-4.0.0 (in progress)
 <li><a href="Allegrocl.html#Allegrocl">Allegro Common Lisp support</a></li>
 <li><a href="Android.html#Android">Android support</a></li>
 <li><a href="CSharp.html#CSharp">C# support</a></li>
-<li><a href="Chicken.html#Chicken">Chicken support</a></li>
 <li><a href="D.html#D">D support</a></li>
 <li><a href="Go.html#Go">Go support</a></li>
 <li><a href="Guile.html#Guile">Guile support</a></li>

Doc/Manual/chapters

@@ -20,7 +20,6 @@ CCache.html
 Allegrocl.html
 Android.html
 CSharp.html
-Chicken.html
 D.html
 Go.html
 Guile.html