This was missing from our original RFC 4447 VPLS implementation. Now
ldpd understands group wildcards as mandated by the RFC, but we still
don't send them ourselves. I can't see any case in which sending a group
wildcard would be useful, but nonetheless this patch provides a function
called lde_send_labelwithdraw_pwid_wcard() which is ready to be used in
the future anytime we feel like it might be useful.
Signed-off-by: Renato Westphal <renato@opensourcerouting.org>