Mark module tun obsolete

[Paul Goyette <paul%whooppee.com@localhost>]

While looking into creating a new module for the tap pseudo-device, I 
noticed that for tun(4) we create both an 'if_tun' module and another 
'tun' module.  The latter of these seems to have no purpose other than 
to require the former.

Perhaps there was a time when the autoload code for network drivers 
would not add the 'if_' prefix to the interface name (ie, autoload would 
only load 'tun').  But in any case that would no longer be necessary, as 
creating a tun interface now properly autoloads the 'if_tun' module.

Therefore, I propose to remove the tun module from the distribution.

Any objections?


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