Connect mitigations(7) to the build

Also add some cross references.

Sponsored by: The FreeBSD Foundation

Remove $FreeBSD$: two-line nroff pattern

Remove /^\.\\"\n\.\\"\s*\$FreeBSD\$$\n/

proccontrol(1): Add wxmap control

Reviewed by: brooks, emaste, markj
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D31779

proccontrol(1): implement 'nonewprivs'

This adds the 'nonewprivs' mode, corresponding to newly added
procctl(2) commands PROC_NO_NEW_PRIVS_CTL and PROC_NO_NEW_PRIVS_STATUS.

Reviewed By: kib
Sponsored By: EPSRC
Differential Revision: https://reviews.freebsd.org/D30940

procctl(8): usermode bits to force LA58/LA57 on exec.

Sponsored by: The FreeBSD Foundation
Differential revision: https://reviews.freebsd.org/D25273

Add implicit PROT_MAX() knob to proccontrol(1).

Reviewed by: emaste, markj (previous version)
Discussed with: brooks
Sponsored by: The FreeBSD Foundation
Differential revision: https://reviews.freebsd.org/D20795

Mention proccontrol(1) -m kpti.

Sponsored by: The FreeBSD Foundation
MFC after: 3 days

Some fixes for proccontrol(1) man page.

- Fix markup.
- Mention that process can only allow tracing for itself. This is already
stated in procctl(2), but requiring knowledge of the syscall description
is too much for the tool user.
- Clearly state that query mode only works for existing process.

Noted and reviewed by: pho
Sponsored by: The FreeBSD Foundation
MFC after: 3 days

proccontrol(1) man page.

Reviewed by: 0mp
Sponsored by: The FreeBSD Foundation
Differential revision: https://reviews.freebsd.org/D19308