Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

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

Fix missing description for command usage

While "jng" or "jib" without arguments told you what each sub-command does,
sub-command usage didn't tell you (e.g., "jng bridge" or "jib addm" gave
only usage and not description).

Comments and fix small bug

Reduce differences between jib/jng and fix a bug that would prevent
additional interfaces from being created if the first of many already
existed (counter wasn't incremented before calling only continue).

Add syntax to disable MAC allocation

Adding `!' before an interface name will disable MAC allocation, falling
back to driver mechanics. Alternatively adding `=' before an interface name
causes the MAC address to be cloned (for ng_bridge(4) back-end only). While
here, disable the auto-detection of wlan* since this knocks the host off;
requiring the host that defines the jail to explicitly enable this feature
by preceding the interface with `='.

Refactor conversion to hex

Centralize MAC derivation formula

Bring generated interfaces up always

Change MAC algo to support mixing w/jng interfaces

Fix bpf unhiding example /etc/devfs.rules

Adjust MAC algo to support interface branching

Adjust MAC allocation algo to support layering

Provide additional information on overall purpose

Fix copy/paste error; s/ngX/eXb/

Add two scripts for vnet jails

One for if_bridge(4) back-end, another for ng_bridge(4) back-end

Sponsored by: FIS Global, Inc.