testing port updates

[Nikolay Sturm <sturm_(_at_)_erisiandiscord_(_dot_)_de>]

As I just got bitten, in case you intend to update a port or test an
update of a port: it is NOT enough to test the new port still packages
or passes regression tests, it is NECESSARY to verify ALL depending
ports also still package (even better test they still work). This is
especially true for library updates.

If you, as a committer, cannot verify this because there are too many
depending ports, run your update through pval, naddy or me for a bulk
build.

Nikolay