This brings the H5VL code in line with the H5I code regarding
naming, parameter order, etc.
Several public API calls were affected by this change.
These changed names to reflect their use with VOL drivers:
H5VLregister() --> H5VLregister_driver()
H5VLregister_by_name() --> H5VLregister_driver_by_name()
H5VLunregister() --> H5VLunregister_driver()
H5VLis_registered() --> H5VLis_driver_registered()
This call was renamed to match H5Iregister(). The order of the first
two parameters also reversed and the object pointer is now const.
H5VLobject_register() --> H5VLregister()
