12/2020 nvc and nvfortran (Nvidia, replaces Portland Group brand)

Wgrib2 will compile with nvc and nvfortran.  The makefile (v3.0.1)
includes support for the Nvidia compilers.  The Nvidia compilers
will also build the wgrib2 shared library.  

   Tested version: x86_linux, Nvidia HPC SDK 20.11