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