libify: Move library sources down into lib directory. A "make" invocation still works from the top-level, but not from down inside the lib directory yet.
Add sha1.c and libsha1.h for doing SHA-1-based message-ID generation. This code comes courtesy of Brian Gladman and Mikhail Gusarov. Both files are available under the GPL and were downloaded as version 0.2 of libsha1 from git://github.com/dottedmag/libsha1.git with the following commit: commit d0f0e7e0dc5ce2d58972cb5a492183c0d4e58433 Author: Mikhail Gusarov <dottedmag@dottedmag.net> Date: Mon Oct 20 22:38:47 2008 +0700 Version bump. Signed-off-by: Mikhail Gusarov <dottedmag@dottedmag.net>