Support for std::time types

[samuknet]

Add support for std::time types e.g. Duration, Instant.

[jdm]

I think we've been limiting the types from std that we support to those that are expected to contain significant heap allocations, like Vec, HashMap, etc., since they involve either making educated guesses or duplicating the internal details of the type. I would not expect the std::time types to fall in that category.