passing variants to dependencies; pre-activate check

[Ryan Schmidt]

On Oct 10, 2015, at 5:33 PM, David Strubbe wrote:

> Specifically, my recently added xcrysden port needs tk +x11 (checked via active_variants), whereas the default is +quartz. As of a couple of weeks ago, I think I was able successfully to trigger installation of tk +x11 when it was not installed by doing 'port install xcrysden +x11'. But now this doesn't happen.

This would only do what you want (i.e. install tk +x11) if tk is not already installed. If tk is already installed (e.g. with +quartz) then the tk installation would not change.