20000418: GB library update

Scott and Steve,

I have uploaded gb.tar.Z to the AS2 upc account.
This tarfile has a modified gbgpds.c routine
along with gbftim.c and gbvlev.c.

The only modifications to gbgpds.c involve creating subroutines
for the long switch statements for the forecast time and
vertical level determination.

By creating the subroutines, I can call them from dcgrib
and avoid the need for the file pointer used in gbgpds,
and hopefully make maintenance of all the case statements
easier.

Let me know if you have questions or problems with these changes.

Thanks,

Steve