Expand EXDC definition

	int number_of_scales;

	//! \brief Type of dielectric functions (<0 at XIP, =0 as function of XI, >0 contants).

	int idfc;

	//! \brief EXDC. QUESTION: better definition?

	//! \brief External medium dielectric constant. QUESTION: correct?

	double exdc;

	//! \brief WP. QUESTION: better definition?

	double wp;