Cipher list selection for OpenSSL

Cipher list selection for OpenSSL

This patch introduces the possibility to arbitrarily select ciphers which
should be promoted resp. declined when establishing a SSL connection
with a client by implementing the new configuration option "CipherList".

By default, OpenSSL would accept low and medium strength and RC-4 ciphers,
which nowadays are known to be broken.

This patch only implements the feature for OpenSSL. A GnuTLS counterpart
has to be implemented in another patch ...

Original patch by Bastian <bastian-ngircd@t6l.de>.

Closes bug #162.