Hi,

Sometimes, I want to unfold all the drawers using `org-fold-show-all',
and then I want to hide them all back. I've noticed, there is a function
`org-fold-hide-drawer-all' does just that, but it's not marked
as a command, so the patch is as simple as adding `(interactive)` there,
as I don't see a reason it shouldn't be one.

-- Ivan