Solution: Install `libtool`. This seems to be the issue, given the CI
output of a recent run, i.e:
```bash
configure.ac:1023: the top level
configure.ac:80: error: possibly undefined macro: AC_LIBTOOL_WIN32_DLL
If this token and others are legitimate, please use m4_pattern_allow.
See the Autoconf documentation.
configure.ac:81: error: possibly undefined macro: AC_PROG_LIBTOOL
configure:7350: error: possibly undefined macro: AC_DISABLE_STATIC
configure:7354: error: possibly undefined macro: AC_ENABLE_STATIC
autoreconf: error: /opt/homebrew/Cellar/autoconf/2.72/bin/autoconf failed with exit status: 1
autogen.sh: error: autoreconf exited with status 1
+ exit 1
```
https://github.com/zeromq/libzmq/actions/runs/9841129190/job/27167025854?pr=4699#step:12:200
* migrate from the old, unmaintained "asciidoc-py" tool to the new "asciidoctor" generator
* migrate from asciidoc-py syntax to the modern Asciidoc syntax (especially page titles and section titles)
* remove the need of "xmlto" utility to create the manpage output; use asciidoctor for that
* add HTML output support to the doc/Makefile by using asciidoctor
* change API documentation files extension from .txt to .adoc to make it more explicit that they are Asciidoc-encoded (as a bonus several IDE plugins will autodetect the .adoc format as Asciidoc)
* remove asciidoc.conf: asciidoctor does not support that; this also required replacing the macro linkzmq into all documentation pages
* add a new Github action CI do deploy to Github Pages the static HTMLs produced by Asciidoctors
* removed references to the "xmlto" and "a2x" tools from the build and packaging systems: Asciidoctor can convert the documentation directly to e.g. pdf (via extended converters) and anyway there was no code/target for using "xmlto" and "a2x" tools anyway
Solution: remove implementation. Frank Hartmann <soundart@gmx.net>,
the author, rejected our request to relicense under MPL2, so we
have to remove his copyrighted work.
Tweetnacl is not security-supported and could not be used in
production environments anyway, the supported backend is libsodium.
Solution: switch to Github Actions
Travis recently started enforcing credits for OSS projects without
any funding. While it is possible to get free credits, it is a manual
step that involves contacting customer support via email and asking to
add them, every week. While this does not require money, it requires
something far scarcer: volunteers time.
Drop Travis and migrate to Github Actions.
