Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Updates for netgraph node manual pages.

Discussed with: glebius
Submitted by: Mamontov Roman <mr.xanto@gmail.com>

Globally replace u_int*_t from (non-contributed) man pages.

The reasoning behind this, is that if we are consistent in our
documentation about the uint*_t stuff, people will be less tempted to
write new code that uses the non-standard types.

I am not going to bump the man page dates, as these changes can be
considered style nits. The meaning of the man pages is unaffected.

MFC after: 1 month

Verify that SYNOPSIS section compiles.

Fixed xref.

Implement minimalistic L2TP sessions statistics and correct man page
for L2TP tunnel statistics (which do not take an argument sessionID).

Reviewed by: archie
Approved by: pjd (mentor)

add a new control message to set sequence numbers on an uninitialized node.

Reviewed by: archie
Approved by: pjd (mentor)

mdoc(7) police: markup overhaul.

Man page for new L2TP netgraph node type.

Obtained from: Packet Design