maint: use gnulib's gitlog-to-changelog instead of a ChangeLog file.

maint: use gnulib's gitlog-to-changelog instead of a ChangeLog file.

* ChangeLog: Removed.
* HACKING (Editing 'ChangeLog'): Removed. Renumbered other sections to
compensate.
* bootstrap.conf (gnulib_modules): Add gitlog-to-changelog.
* Makefile.am (ChangeLog): Generate the ChangeLog for 2011...
(dist-hook): ...from the output of `git log' before rolling a
distribution tarball.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>