A-Netz: Click removal when changing sequenced paging tones

When tone changes to next tone, a transition of 2ms is performed. The last
tone is faded out and the new tone faded in.

src/anetz/anetz.h

@@ -38,6 +38,7 @@ typedef struct anetz {
 	double			paging_phase256[4];	/* current phase */
 	int			paging_tone;		/* current tone (0..3) in sequenced mode */
 	int			paging_count;		/* current sample count of tone in seq. mode */
+	int			paging_transition;	/* set to number of samples during transition */
 } anetz_t;