master: fix some xrst --external_links errors.

Author: bradbell

appendix/whats_new/2006.xrst

@@ -258,7 +258,7 @@ Fix compiler warning while compiling ``cppad/RombergOne/``
 Cygwin packages, and other system packages,
 should not have a dash in the version number.
 See
-`cygwin package file naming <http://www.cygwin.com/packaging-package-files.html#naming>`_ .
+`cygwin package file naming <https://cygwin.com/packaging-package-files.html>`_ .
 or, to quote the
 `rpm file naming convention <http://ftp.rpm.org/max-rpm/ch-rpm-file-format.html>`_
 *The only restriction placed on the version is that*

appendix/whats_new/2024.xrst

@@ -410,7 +410,7 @@ were unable to reproduce in an automated regression test;
 see comment that starts with 2024-02-14 in
 `include/cppad/local/optimize/match_op.hpp` .
 
-.. _speed.py: https://dismod-at.readthedocs.io/user_speed.py.html
+.. _speed.py: https://dismod-at.readthedocs.io/latest/user_speed.py.html
 
 01-16
 =====

test_more/general/simple_vector.cpp

@@ -18,7 +18,6 @@ Old simple vector example now used just for validation testing
 // # include <valarray>
 // # define MySimpleVector std::valarray
 
-// Assuming CppAD (http://www.seanet.com/~bradbell/cppad) is installed
 # include <cppad/utility/vector.hpp>
 # define MySimpleVector CppAD::vector
 

user_guide.xrst

@@ -47,7 +47,7 @@ Versions
    * - Documentation for most recent stable version
      - `stable-2025 <https://cppad.readthedocs.io/stable-2025>`_
    * - Most recent release of this stable version
-     - `release-2025 <https://github.com/coin-or/CppAD/archive/20250000.0.tar.gz>`_
+     - `release-2025 <https://codeload.github.com/coin-or/CppAD/tar.gz/refs/tags/20250000.0>`_
 
 {xrst_comment END: Before changing see new_release.sh and check_version.sh}
 
@@ -61,7 +61,7 @@ Other Links
      - :ref:`get_started<get_started.cpp-name>`
      - :ref:`whats_new-name`
      - :ref:`addon-name`
-     - `project manager <http://www.seanet.com/~bradbell>`_
+     - `project manager <https://www.seanet.com/~bradbell/>`_
 
 
 Algorithmic Differentiation
@@ -188,7 +188,7 @@ Software Engineering
 ********************
 CppAD is developed using the software engineering procedures described
 on the project manager's
-`software <http://www.seanet.com/~bradbell/software.html>`_
+`software <https://www.seanet.com/~bradbell/software.html>`_
 web page.
 
 Testing