Note that it is not really a circular buffer in this case, but
a full reset of the buffer to the beginning. This matches the
documentation, but it seems valuable to add an explicit test for
this case.
In some cases the license-identification header was missing,
so I added that as well. Replaced the remaining headers that
specifically identified "Versions 3.13.7 and higher".
Makefiles and the build system were deliberately excluded.
