MFC r312443:
mppc - Finish pluging NETGRAPH_MPPC_COMPRESSION.

There were several places where reference to compression were left
unfinished. Furthermore, KASSERTs contained references to MPPC_INVALID
which is not defined in the tree and therefore were sure to break with
INVARIANTS: comment them out.

Reported by: Eugene Grosbein
PR: 216265

MFC r266538:
Make ng_mppc to not disable the node in case of multiple packet loss.
Quite often it can be just packet reorder, and killing link in such case
is inconvenient. Add few sysctl's to control that behavior.

PR: kern/182212
Submitted by: Eugene Grosbein <egrosbein@rdtc.ru>

MFC r266538:
Make ng_mppc to not disable the node in case of multiple packet loss.
Quite often it can be just packet reorder, and killing link in such case
is inconvenient. Add few sysctl's to control that behavior.

PR: kern/182212
Submitted by: Eugene Grosbein <egrosbein@rdtc.ru>