of the va_list, so it's at least possible for another connector to know what
the operation is and decide whether to implement it or not.
Added a new VOL sub-class called "introspect" where callbacks that report
information about the connector or container can be placed. Added an
'opt_query' callback to this sub-class, for a connector to report back
to the library whether a particular optional callback operation is supported.
Also added a 'get_conn_cls' introspection callback, to retrieve the H5VL_class_t
of a connector (either the "current" connector, H5VL_GET_CONN_LVL_CURR, or
the terminal connector, H5VL_GET_CONN_LVL_TERM).
Moved the "post open" operation from a file 'specific' operation to a file
'optional' operation, now that it's possible to detect (with the 'opt_query'
introspection callback) whether a VOL connector implements an optional
operation, without just returning an error.
Added new internal VOL helper routines: H5VL_object_is_native, to determine
if an object is in (or is a) native file, and H5VL_file_is_same, to determine
if two objects are in (or are) the same terminal VOL connector's container.
(And moved the special handling for FILE_IS_EQUAL operation out of internal VOL
callback routine into H5VL_file_is_same)
Made new dataset 'get' operation for H5Dvlen_get_buf_size, aligning it better
with other 'get' operations in API.
Fixed several issues with pass-through connectors, which are now passing the
'make check-passthrough-vol' tests again.
A bunch of warning and style cleanups as well.
* H5VLconnector.h for terminal connector things
* H5VLconnector_passthru.h for passthrough connector things
Note that these headers are arranged such that they are included in
hdf5.h so VOL connectors only need to include that. The separation into
multiple headers is mainly for readability.
