Allow parallel writes to use zlib

[edwardhartnett]

Fixes #1580

[WardF]

Is there a minimum version of HDF5 required to support this? Or is it a feature that just has been available in parallel HDF5 but not enabled in netCDF?

[gsjaardema]

I know that 1.10.3 and 1.10.4 had bugs that caused "Too many communicators" failures that was fixed in 1.10.5.

[gsjaardema]

Looks like parallel compression output was released in 1.10.2:

In the past, HDF5 parallel applications could read compressed data, but couldn’t create and write data using compression and other filters like Fletcher32 for raw data checksum. This restriction was removed in HDF5 1.10.2. 

[WardF]

@gsjaardema thanks! @edwardhartnett I think we need to find a way to fencepost this so that it doesn't break builds for people still using older versions of libhdf5.

[edwardhartnett]

Yes, I should have made it clear that this PR is not quite ready to merge. I just wanted to try it on the CI.

I would like to:

• Add more tests.
• Better handle cases of older HDF5
• See if this also applies to fletcher32 (for completeness - I don't think many people use fletcher32.)

[edwardhartnett]

I'm just going to take this down while I work on it a bit more. I will put up a complete PR in a bit.