Make autoreconf -i -v happy

This requires adding empty AUTHORS and ChangeLog files (for now),
as well as an empty COPYING until the right license text is recovered.

ftp://athena-dist.mit.edu/pub/ATHENA/hesiod/README suggests the license
is MIT, but offers slightly different text:

Copyright 1993-1997 by the Massachusetts Institute of Technology.

Project Athena, Athena, Athena MUSE, Discuss, Hesiod, Kerberos, Moira,
OLC, X Window System, and Zephyr are trademarks of the Massachusetts
Institute of Technology (MIT).  No commercial use of these trademarks
may be made without prior written permission of MIT.

Also, install m4/.empty so that git creates the directory.
Add autogen.sh
Add .gitignore files