Disable Modula3 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

@@ -120,7 +120,6 @@ SWIGJAVASCRIPT                  Defined when using Javascript
 SWIG_JAVASCRIPT_JSC             Defined when using Javascript for JavascriptCore
 SWIG_JAVASCRIPT_V8              Defined when using Javascript for v8 or node.js 
 SWIGLUA                         Defined when using Lua
-SWIGMODULA3                     Defined when using Modula-3
 SWIGMZSCHEME                    Defined when using Mzscheme
 SWIGOCAML                       Defined when using Ocaml
 SWIGOCTAVE                      Defined when using Octave

Doc/Manual/SWIG.html

@@ -129,7 +129,6 @@ Supported Target Language Options
      -java           - Generate Java wrappers
      -javascript     - Generate Javascript wrappers
      -lua            - Generate Lua wrappers
-     -modula3        - Generate Modula 3 wrappers
      -mzscheme       - Generate Mzscheme wrappers
      -ocaml          - Generate Ocaml wrappers
      -octave         - Generate Octave wrappers

Doc/Manual/Sections.html

@@ -50,7 +50,6 @@ Last update : SWIG-4.0.0 (in progress)
 <li><a href="Javascript.html#Javascript">Javascript support</a></li>
 <li><a href="Lisp.html#Lisp">Common Lisp support</a></li>
 <li><a href="Lua.html#Lua">Lua support</a></li>
-<li><a href="Modula3.html#Modula3">Modula3 support</a></li>
 <li><a href="Mzscheme.html#Mzscheme">MzScheme/Racket support</a></li>
 <li><a href="Ocaml.html#Ocaml">Ocaml support</a></li>
 <li><a href="Octave.html#Octave">Octave support</a></li>

Doc/Manual/chapters

@@ -28,7 +28,6 @@ Java.html
 Javascript.html
 Lisp.html
 Lua.html
-Modula3.html
 Mzscheme.html
 Ocaml.html
 Octave.html