unused variables

Thanks for the project.

```
>gfortran -c -Wextra -Wall ogpf.f90
ogpf.f90:1348:20:

 1348 |          integer:: j
      |                    1
Warning: Unused variable 'j' declared at (1) [-Wunused-variable]
ogpf.f90:1345:22:

 1345 |          integer:: ncx
      |                      1
Warning: Unused variable 'ncx' declared at (1) [-Wunused-variable]
```