Three bugs and missing features are fixed here:
- pp_open_globals received a SEGFAULT because its rt_opts parameter was not
correctly handled when NULL;
- use ppg->nlinks instead of obsolete ppg->nports;
- set def->slaveOnly and def->clockQuality.clockClass properly even when
more than one link is defined

Signed-off-by: Aurelio Colosimo <aurelio@aureliocolosimo.it>