Test: add documentation and rebuild files

Test: add documentation and rebuild files

One certificate in test folder is already expired, other
will follow.
The original private keys to rebuild the certificates are
not available, so no way to re-sign the same certificates.

Document why and how the test is performed.
Put in a Makefile the whole set of commands to rebuild
the certificates and encrypt the binary test.
Replace all the certificates and the encrypted binary
with new versions.

New certificates will expire in 2033.

OpenSSL is required only to re-build the certificates.
No need for OpenSSL to compile VPNC or to run the test.

Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
git-svn-id: https://svn.unix-ag.uni-kl.de/vpnc/trunk@539 315857ad-0bdb-0310-b42e-dec37551a5f0