Remove obsolete documentation build tools for Windows

The scripts and instructions have been nonfunctional at least since
PostgreSQL 10 (commit 510074f) and
nobody has stepped up to fix them.  So right now just remove them until
someone wants to resurrect them.

Discussion: https://www.postgresql.org/message-id/flat/B74C0219-6BA9-46E1-A524-5B9E8CD3BDB3%40yesql.se

Author: petere

doc/src/sgml/install-windows.sgml

@@ -486,52 +486,5 @@ $ENV{PERL5LIB}=$ENV{PERL5LIB} . ';c:\IPC-Run-0.94\lib';
   </para>
  </sect2>
 
- <sect2>
-  <title>Building the Documentation</title>
-
-  <para>
-   Building the PostgreSQL documentation in HTML format requires several tools
-   and files. Create a root directory for all these files, and store them
-   in the subdirectories in the list below.
-   <variablelist>
-    <varlistentry>
-     <term>OpenJade 1.3.1-2</term>
-     <listitem><para>
-      Download from
-      <ulink url="http://sourceforge.net/projects/openjade/files/openjade/1.3.1/openjade-1_3_1-2-bin.zip/download"></ulink>
-      and uncompress in the subdirectory <filename>openjade-1.3.1</filename>.
-     </para></listitem>
-    </varlistentry>
-
-    <varlistentry>
-     <term>DocBook DTD 4.2</term>
-     <listitem><para>
-      Download from
-      <ulink url="http://www.oasis-open.org/docbook/sgml/4.2/docbook-4.2.zip"></ulink>
-      and uncompress in the subdirectory <filename>docbook</filename>.
-     </para></listitem>
-    </varlistentry>
-
-    <varlistentry>
-     <term>ISO character entities</term>
-     <listitem><para>
-      Download from
-      <ulink url="http://www.oasis-open.org/cover/ISOEnts.zip"></ulink> and
-      uncompress in the subdirectory <filename>docbook</filename>.
-     </para></listitem>
-    </varlistentry>
-   </variablelist>
-   Edit the <filename>buildenv.pl</filename> file, and add a variable for the
-   location of the root directory, for example:
-<programlisting>
-$ENV{DOCROOT}='c:\docbook';
-</programlisting>
-   To build the documentation, run the command
-   <filename>builddoc.bat</filename>. Note that this will actually run the
-   build twice, in order to generate the indexes. The generated HTML files
-   will be in <filename>doc\src\sgml</filename>.
-  </para>
- </sect2>
-
  </sect1>
 </chapter>

src/tools/msvc/README

@@ -47,7 +47,6 @@ arguments.
 
 - User tools -
 build.pl               tool to build the binaries
-builddoc.pl            tool to build the docs
 clean.bat              batch file for cleaning up generated files
 install.pl             tool to install the generated files
 mkvcbuild.pl           tool to generate the Visual Studio build files