build: enable git-version-gen, automake silent rules, generate ChangeLog

build: enable git-version-gen, automake silent rules, generate ChangeLog

* configure.ac (AC_INIT): Use git-version-gen.
Use AM_SILENT_RULES([yes]).
(AM_INIT_AUTOMAKE): Drop gnits; conflicts with git-version-gen versions.
* bootstrap.conf (gnulib_modules): Use getopt-gnu
Ensure ChangeLog exists, for automake.
rather than obsolete "getopt" module.
Add gitlog-to-changelog.
Add git-version-gen.
Add gnu-make, gnumakefile and maintainer-makefile.
* Makefile.am (dist-hook, gen-ChangeLog): New rules, to generate
ChangeLog and insert it into the distribution tarball.
(EXTRA_DIST): Add ChangeLog-2007.