credits.php: Add package versions where available.

[bpfoley]

And include versions for the pinc/3rdparty imports

Useful for figuring out what's deployed to a sandbox.

See sandbox at https://www.pgdp.org/~bfoley/c.branch/credits-version/credits.php

[cpeel]

I realize it's security through obscurity, but I'm wary of advertising the version on the prod. Thoughts about limiting it just to $testing=true?

[bpfoley]

I realize it's security through obscurity, but I'm wary of advertising the version on the prod. Thoughts about limiting it just to $testing=true?

Sure. No objections. Testing is the place it's most likely to be useful anyway: where we're trying to keep track of any number of sandboxes.