Automatic FSK polarity selection on TX side

This is done by simulating two cells with different polarities.
On first message from mobile station, the cell with the correct
polarity is used, the other is disabled.

On RX side the polarity is not selected, since FSK decoder detects
polarity for every frame.

src/cnetz/sysinfo.h

@@ -1,6 +1,6 @@
 
 typedef struct system_information {
-	uint32_t	ogk_timeslot_mask;	/* each bit defines an assigned time slot */
+	int		flip_polarity;		/* use negative polarity for FSK transmission */
 	uint8_t		fuz_nat;		/* national network ID */
 	uint8_t		fuz_fuvst;		/* id of switching center */
 	uint8_t		fuz_rest;		/* rest of base station id */
@@ -18,7 +18,7 @@ typedef struct system_information {
 	uint8_t		reduzierung;
 } cnetz_si;
 
-extern cnetz_si si;
+extern cnetz_si si[];
 
 void init_sysinfo(void);