Example 7. Locating a Vdata Containing Specific Field Names

This example illustrates the use of VSgetid/vsfgid to obtain the reference
number of each vdata in an HDF file and the use of VSfexist/vsfex to
determine whether a vdata contains specific fields.

In this example, the program searches the HDF file "General_Vdatas.hdf"
to locate the first vdata containing the fields "Position" and
"Temperature".  The HDF file is an output of the program in Example 3.

