docs/175712: Update 'disk naming' handbook page

[a]

>Number:         175712
>Category:       docs
>Synopsis:       Update 'disk naming' handbook page
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-doc
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Wed Jan 30 21:10:00 UTC 2013
>Closed-Date:
>Last-Modified:
>Originator:     a
>Release:        9.1
>Organization:
>Environment:
-
>Description:
The handbook should mention the new disk naming convention 'ada'.

http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/disks-naming.html
>How-To-Repeat:

>Fix:


>Release-Note:
>Audit-Trail:
>Unformatted: