MFH: 285685
Add support to the jail framework to be able to mount linsysfs(5) and linprocfs(5).

PR: 207179
Requested by: thomas@gibfest.dk
Reviewed by: jamie, bapt
Approved by: re (gjb)
Sponsored by: gandi.net
Differential Revision: https://reviews.freebsd.org/D5390