maint: distribute a single ChangeLog file.

maint: distribute a single ChangeLog file.

* ChangeLog.1996, ChangeLog.1997, ChangeLog.1998, ChangeLog.1999,
ChangeLog.2000, ChangeLog.2001, ChangeLog.2002, ChangeLog.2003,
ChangeLog.2004, ChangeLog.2005, ChangeLog.2006, ChangeLog.2007,
ChangeLog.2008, ChangeLog.2009, ChangeLog.2010: Remove.  Content
moved from here...
* ChangeLog.old: ...to here.
* Makefile.am (EXTRA_DIST): Update list of ChangeLog files.
(changelog_old): New variable to hold path to ChangeLog.old file.
($(changelog)): Update to concatenate non-distributed
ChangeLog.old file to distributed ChangeLog after git log entries.

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