Reimplement control part of npppd(8) with imsg. Also add "monitor"
command for npppctl(8) to monitor PPP session start/stop events.

Fix comments and styles. Delete unused variables and labels.
No binary changes.

ok mcbride henning

Replace npppdctl(8) by new npppctl(8). npppctl was written from
scratch, it uses parser.c derived from ikectl(8) to have OpenBSD's
fashion. This includes related changes listed below:
- changed npp

Replace npppdctl(8) by new npppctl(8). npppctl was written from
scratch, it uses parser.c derived from ikectl(8) to have OpenBSD's
fashion. This includes related changes listed below:
- changed npppd control IPC heavyly.
- support IPv6 as tunnel source address.
- deleted support changing the configuration of npppd_ctl on running.
Because it is not so needed but it requires privilege operations.
- refactors.

man page helps from jmc. tested by sebastia.
ok deraadt sebastia sthen

show more ...