Ticket #150 (enhancement)

If the user asks to configure a particular component, and that component depends on something else in the tree that isn't already being built, enable the required component(s) automatically.

I think this should be implemented by some simple tsort-style dependency chain. This is orthogonal to the request from the NetBSD folks to be able to build components against installed components.

The existing in-tree dependency checking is a bit of a kludge and ought to be reworked as part of the solution to this issue.