MFC r228237:
> Add a screen that asks if the user would like to enable crash dumps,
> giving them a very brief description of the trade-offs. Whether the
> user opts in or out add an entry to what will become /etc/rc.conf
> explaining what dumpdev is and how to turn on/off crash dumps. The folks
> who handle interacting with users submitting PRs have asked for this.
>
> Reviewed by: nwhitehorn
Approved by: re (kib)
git-svn-id: svn://svn.freebsd.org/base/releng/9.0@228238
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