merge r2995, r2996, r2997, r2998, r3003, r3141, r3210, r3211, r3232: various SSL fixes and features: *) $ssl_client_verify *) "ssl_verify_client ask" was changed to "ssl_verify_client optional" *) ssl_crl *) delete OpenSSL pre-0.9.7 compatibility: the sources were not actually compatible with OpenSSL 0.9.6 since ssl_session_cache introduction *) fix memory corruption in $ssl_client_cert *) issue SNI warning instead of failure: this is too common case *) use ngx_log_error(), since OpenSSL does not set an error on the failure *) add SNI support in -V output