Add interface for logical in Fortran

[lxavier]

PGF90-S-0155-Could not resolve generic procedure fs_write_field

call fs_write_field(ppser_serializer, ppser_savepoint, 'scale_fac_index', scale_fac_index)

[clementval]

@lxavier Yeah at the moment there is no interface for logical ... still need to do the trick as it was with the old dumper. But it would be nice to have it.

[havogt]

@clementval This is fixed, right?