- Change the "jail_" prefix for internal script variables. This fixes an

- Change the "jail_" prefix for internal script variables. This fixes an
issue where some global jail_* variables were overriden in the script. [1]
- Change "jid" to "jname" in rc.conf(5), since it's more a jail name than a
jail id. [1]
- Update examples and comments in defaults/rc.conf to advertise new
variables and the fact that some of the jail-specific variables may be made
jail-global. [2]

Reported by:	pjd [1], clsung [2]
Approved by:	cperciva
X-MFC after:	i got sufficient testing from people using rc.d/jail