Array lengths should be explicit in fortran interface

[jhp-lanl]

Much (if not all) of the fortran interface currently uses function signatures that look like

integer function fun_f(val, array_vals) result(err)
    integer, value, intent(in) :: val
    integer, dimension(:), target, intent(inout) :: array_vals

    err = fun(val, c_loc(array_vals))

where the dimension of the dummy variable is not explicitly defined. Since all that's passed over the C++ side is the pointer to the array, it is very easy for the array to be under-allocated and go out of bounds.

In particular, if we choose to change the length of array_vals on the C++ side, we have no way of alerting the Fortran host codes that the length has changed and they need to allocate more space.

I think it would be better if our interface dummy arguments use explicit lengths so that fortran can do length checking at compile time. Then the interface will look like

integer function fun_f(val, array_vals) result(err)
    integer, value, intent(in) :: val
    integer, dimension(4), target, intent(inout) :: array_vals

    err = fun(val, c_loc(array_vals))

This will produce a compile-time error if the host code tries to pass an array in that doesn't comply with the API we've defined:

Error: Actual argument contains too few elements for dummy argument 'array_vals' (2/4) at (1)

@dholladay00 this would fix some UB I saw in the xRAGE interface