Merge all of my changes from merge-back-to-feature-vfd_swmr-attempt-1,

including the merge of `hdffv/hdf5/develop`, back to the branch that Vailin and
I share.

Now I need to put this branch on a fork with a less confusing name than
vchoi_fork!

tools/test/h5stat/testfiles/h5stat_help2.ddl

@@ -23,3 +23,13 @@ Usage: h5stat [OPTIONS] file
      -s, --freespace       Print free space information
      -S, --summary         Print summary of file space information
      --enable-error-stack  Prints messages from the HDF5 error stack as they occur
+     --s3-cred=<cred>      Access file on S3, using provided credential
+                           <cred> :: (region,id,key)
+                           If <cred> == "(,,)", no authentication is used.
+     --hdfs-attrs=<attrs>  Access a file on HDFS with given configuration
+                           attributes.
+                           <attrs> :: (<namenode name>,<namenode port>,
+                                       <kerberos cache path>,<username>,
+                                       <buffer size>)
+                           If an attribute is empty, a default value will be
+                           used.