Good catch.  Yes, `actnum_kw` certainly needs to be `int`.  The keyword data is stored (in the admittedly moribund `EclipseGridParser` class) as a `std::vector<int>` and the implementation of function `ecl_grid_alloc_GRDECL_kw()` does appear to require an `int` too.  Of course, you're the authority on *that* one.