docs: move chapter on automake history out of main manual

docs: move chapter on automake history out of main manual

The chapter on Automake history, while certainly interesting and
even fascinating, does not truly pertain to a reference manual,
so move it out from there and into its own dedicated file.  This
change is made more advisable and pressing by the fact that such
and "Automake history" chapter hasn't been updated since the 1.9.6
release, so it has been becoming less faithful and useful since
then.

* doc/history.texi: New, manual on the history of the automake
package; extracted from ...
* doc/automake.texi: ... this file, with related adjustments.
* doc/Makefile.am (info_TEXINFOS): Add 'history.texi'.
(history_TEXINFOS): New, list included file 'fdl.texi'.
* Makefile.am (release-stats): Remove as obsolete.
* HACKING (Release Procedure): Don't advise anymore to run the
"release-stats" target and to update the manual with its output.
* NEWS: Update.
* .gitignore: Likewise.