AM: scm_from_pointer() interface added
AM: scm_from_c_funptr() return a pointer object

Not and exact integer as before  --- Guile 2.0 has a dedicated pointer
object type.
AM: call bgy3d_init() and bgy3d_finalize() now that bgy3d.f90 has them

See ham_calc_module.f90 for another use of WITH_BGY3D_NON_GPL which,
if replaced by WITH_BGY3D will have an effect of unconditionally
calling bgy3d code every SCF iteration.