Stop iswitchb tag completion from including virtual files

Stop iswitchb tag completion from including virtual files

Tassilo Horn writes:

> When I want to set a tag using `C-c C-q TAB' I get a iswitchb completion
> prompt, cause org-completion-use-iswitchb is t.  I also use iswitchb's
> virtual files feature (iswitchb-use-virtual-buffers set to t), which
> includes files that aren't opened in a buffer, but are in the recentf
> list.  This is a cool thing when switching buffers (I barely use C-x C-f
> anymore and switch to the virtual buffer instead), but totally useless
> and annoying for tab completion in org.
>
> So when completing anything (files/tags/...) in org with iswitchb,
> switchb-use-virtual-buffers should be let-bound to nil before.