Basic SSL support has been added. This the very first, rough version (may contain bugs).
Current features (these should work):
 * Connect via SSL
 * Two-side X.509 certificate-based authentication
 * Certificate verification: OpenSSL built-in + SNI (based on subject's CN(s))
 * Supports encrypted private key files
 * CRL support (CRL file must be specified)
 * Supports PEM format
 * Session resumption is not supported yet
 * OCSP is not supported yet
 * Reports errors via ctx->last_ssl_error (and errno sometimes)

The source code is not yet properly formatted (indented). Tests should pass (tested on MongoDB v2.6.0 Debian Wheezy) when CRL file is omitted. See TODO and tests more information.