Example 1. Creating an HDF File and Vgroups

This example illustrates the use of Hopen/hopen, Vstart/vfstart, Vattach/vfatch,
Vdetach/vfdtch, Vend/vfend, and Hclose/hclose to create and to access
two vgroups in an HDF file.

The program creates the HDF file, named "Two_Vgroups.hdf", and two
vgroups stored in the file.  Note that, in this example, the program
only creates two empty vgroups.