gitlog-to-changelog: Copyright-paperwork-exempt: yes == (tiny change)

gitlog-to-changelog: Copyright-paperwork-exempt: yes == (tiny change)

* build-aux/gitlog-to-changelog (main): Map the string, at beginning
of line in a git commit log, "Copyright-paperwork-exempt: yes", to
the "  (tiny change)" notation that is appended to the standard
ChangeLog "date  name  email" header line.