Allow non standard cert dir

ixwebsocket/IXSocketOpenSSL.cpp

@@ -506,7 +506,7 @@ namespace ix
                 else
                 {
                     if (SSL_CTX_load_verify_locations(
-                            _ssl_context, _tlsOptions.caFile.c_str(), NULL) != 1)
+                            _ssl_context, _tlsOptions.caFile.c_str(), IXWEBSOCKET_OPEN_SSL_CERTS) != 1)
                     {
                         auto sslErr = ERR_get_error();
                         errMsg = "OpenSSL failed - SSL_CTX_load_verify_locations(\"" +