* bootstrap.conf: Request the latest gnulib stable branch.
* README.git: Recommend the argument form of autogen/autopull.
* bootstrap: Import the latest version of bootstrap.
* bootstrap-funclib.sh: Ditto.
* autogen.sh: Ditto.
* autopull.sh: Ditto.
* README.git: Document the changes.
* bootstrap.conf: Set GNULIB_REVISION to avoid random updates.
* configure.ac: Set the minimum autoconf version back to 2.69:
that's the most common version deployed today, and it still works.
* bootstrap: Copy the latest from gnulib.
* autogen.sh: Ditto.
* autopull.sh: Ditto.
* bootstrap-funclib.sh: Ditto.