Depreciate and remove gbde

[Slawa Olhovchenkov]

On Mon, Oct 19, 2015 at 01:52:05AM -0700, Perry Hutchison wrote:

> Anton Shterenlikht <mexas at bris.ac.uk> wrote:
> 
> > I use gbde.
> > Can switch to geli, if required,
> > but please provide detailed instructions
> > for switching before removing gbde.
> 
> Such instructions would presumably be included in the UPDATING
> entry.
> 
> An additional consideration:  If there is no convert-in-place
> mechanism -- i.e. the only way to convert a gbde FS to geli is to
> backup, wipe, and restore (thus involving considerable downtime)
> -- it will give some unknown number of production users a strong
> motivation to freeze at [last version of FreeBSD to include gbde
> support].

This must be show-stoper for removing gbde.