autogen: work with older libtool and autoconf
autogen: work with older libtool and autoconf

wurenny/pgbouncer-x2,digoal/pgbouncer-x2,kvap/pgbouncer,dbaxa/pgbouncer,wurenny/pgbouncer-x2,jaiminpan/pgbouncer,jaiminpan/pgbouncer,digoal/pgbouncer-x2,kvap/pgbouncer,digoal/pgbouncer-x2,digoal/pgbouncer-x2,kvap/pgbouncer,jaiminpan/pgbouncer,dbaxa/pgbouncer,jaiminpan/pgbouncer,dbaxa/pgbouncer,dbaxa/pgbouncer,wurenny/pgbouncer-x2,kvap/pgbouncer,wurenny/pgbouncer-x2