freetdm: add missing string for SIGEVENT_RELEASED

libs/freetdm/src/include/freetdm.h

@@ -301,7 +301,7 @@ typedef enum {
 	FTDM_SIGEVENT_COLLISION, /*!< Outgoing call was dropped because an incoming call arrived at the same time */
 	FTDM_SIGEVENT_INVALID
 } ftdm_signal_event_t;
-#define SIGNAL_STRINGS "START", "STOP", "UP", "FLASH", "PROGRESS", \
+#define SIGNAL_STRINGS "START", "STOP", "RELEASED", "UP", "FLASH", "PROGRESS", \
 		"PROGRESS_MEDIA", "ALARM_TRAP", "ALARM_CLEAR", \
 		"COLLECTED_DIGIT", "ADD_CALL", "RESTART", "SIGSTATUS_CHANGED", "COLLISION", "INVALID"