Import net/unbound package from Subversion

This is an import of the net/unbound package from Subversion revision 40658 (May 2, 2014). The only change is the addition of PKG_LICENSE and PKG_LICENSE_FILE to Makefile. Unbound 1.4.22 is the current upstream release.

Given that this is an unchanged package, has been working well for me with trunk versions of Barrier Breaker, and that I would really like to see it being included in the packages automatically built for 14.07, I propose to merge this on the `for-14.07` branch. If and when merged I'll follow-up with a merge commit from `for-14.07` to `master`.