HDF5 1.10.1 solves network file problem on Mac OS

Here is a positive test result for HDF5 release 1.10.1-pre2. With HDF5
1.10.0 (and patch1) on Mac OS, all access to NFSv3-mounted files would fail
due to the previously reported flock problem. In plainer terms, HDF5
1.10.0 was not able to read or write any files on network file servers.
This was due to a deficiency in NFSv3 support for Mac OS.

This problem was solved in 1.10.1 pre-releases. HDF5 support added a fix
that disabled file locking behavior, thus avoiding the problem. Please see
details in the release notes starting with 1.10.1-pre2, under "Other New
Features".

https://gamma.hdfgroup.org/ftp/pub/outgoing/hdf5/hdf5-1.10.1-pre2-RELEASE.txt

The fix is not a build fix, rather it is a run time environment variable
setting. This is versatile. File locking can be used with local files,
and disabled only when necessary to access network files.

On a more mundane note, HDF5 1.10.1-pre2 compiled and passed all make check
tests on my desktop Mac, OS X El Capitan version 10.11.6.

Thanks to the HDF5 Group for providing the flock fix. This will allow my
work group and other Mac users to advance past HDF5 1.8.

--Dave Allured
NOAA/OAR/ESRL/PSD/CIRES