devel/autoconf*: restructure to prepare for 2.71
- Rename autoconf 2.13 port directory, package, and command all to
autoconf2.13 just like ports like perl and python.
- Let USES=autoreconf run gtkdocize if necessary.
- Rewrite autoconf-wrapper and rename it autoconf-switch to reflect
better what it does.
- Delete patch-bison. It has been reverted upstream.
- Add a patch to let autoreconf set the AUTOCONF environment variable
so subprocesses like automake use the correct version.
- Make building of info files optional.
- Address portlint, portclippy, portfmt issues in devel/autoconf*.
PR: 259556, 263970