devel/gprbuild: Upgrade version 20150506 => 20160609

GPRBuild build is now hosted on github, so we can move away from the
yearly releases and update more frequently. Unfortunately the docs
makefile is currently broken so docs are disabled currently. When
they come back, only txt and html docs will be supported.

This new version detected a missing reference in the template-parser
port so that port has been fixed and the downstream ports bumped
accordingly.

It also discovered an interface specification issue in a designer
example of qtada. I spent a few minutes trying to fix/workaround it,
but ultimately marked it broken. I will also deprecate the port because
it no development has occurred since the port was created, and it's not
even based on a real release. We'll see if anybody cares (3 month
deprecation).