re: Issue https://github.com/Unidata/netcdf-c/issues/1848
The existing Virtual File Driver built to support byte-range
read-only file access is quite old. It turns out to be extremely
slow (reason unknown at the moment).
Starting with HDF5 1.10.6, the HDF5 library has its own version
of such a file driver. The HDF5 developers have better knowledge
about building such a driver and what incantations are needed to
get good performance.
This PR modifies the byte-range code in hdf5open.c so
that if the HDF5 file driver is available, then it is used
in preference to the one written by the Netcdf group.
Misc. Other Changes:
1. Moved all of nc4print code to ncdump to keep appveyor quiet.
