maint: add gitlog-to-changelog.
maint: add gitlog-to-changelog.

Hand maintaining a ChangeLog is tedious.
* build-aux/gitlog-to-changelog: New file.

Signed-off-by: Gary V. Vaughan <f9023000f29773649f3850298becb9544b5fd6a9@gnu.org>

GUI/lyaml,GUI/lyaml