The other time stuff is higher-level

Containers were using crypto_digest.h, just to see the value of
DIGEST_LEN.  Moved those constants into a new defs module.

Minimizing includes revealed other places includes were necessary.

Includes configuration files to enforce these rules on lib and
common.  Of course, "common" *is* a modularity violation right now,
so these rules aren't as strict as I would like them to be.

You have no idea how glad I am that this is automated.

I am calling the crypto library "crypt_ops", since I want
higher-level crypto things to be separated from lower-level ones.
This library will hold only the low-level ones, once we have it
refactored.

This one has no generated code.

Apparently it has no testing variant.