#48 xmlrpc_server_abyss: use va_args properly

[Igor Gnatenko]

../src/xmlrpc_server_abyss.c: In function ‘createServer’:
../src/xmlrpc_server_abyss.c:783:13: error: format not a string literal and no format arguments [-Werror=format-security]
             xmlrpc_faultf(envP, error);
             ^~~~~~~~~~~~~

[Yegor Yefremov]

This change is already upstream. See this revision.