vdata_id	IN:	Vdata identifier returned by VSattach
	vdata_class	IN:	Name of the vdata class

	Purpose	Sets the class name of a vdata.
	Return value	Returns SUCCEED (or 0) if successful and FAIL (or -1) otherwise.
	Description	VSsetclass sets the class name of the vdata identified by the parameter vdata_id to the value of the parameter vdata_class.
		At creation, the class name of a vdata is NULL. The class name may be reset more than once. Class names, like vdata names, can be any character string. They exist solely as meaningful labels to user applications and are not used by the HDF library in any way. Class names will be truncated to VSNAMELENMAX (or 64) characters.

	FORTRAN	integer function vsfscls(vdata_id, vdata_class)
		integer vdata_id
		character*(*) vdata_class