Intel oneAPI compilers

Support for the new Intel LLVM-based compilers starts with wgrib2 v3.1.2.
Prior versions may compile but will have problems with the simple unpacking.
Wgrib2 v3.1.2 changed the code for simple unpacking so that it works with
all compilers including oneAPI. Wgrib2 v3.1.3 fixes openmp compile.

To compile wgrib2 using bash and linux

export CC=icx
export FC=ifx
export COMP_SYS=oneapi_linux           optional on linux
make clean
make                                   optional, generate wgrib2 executable
make lib                               optional, generate wgrib2 library


The oneAPI compilers have not been tested with Windows. Currently support
or windows is limited to the cygwin gcc/gfortran compilers.

The "COMP_SYS=oneapi_linux" may not work in windows because the compiler
options may differ between windows and linux.