freetdm: multiple fixes for the core and analog

* Replace ftdm_channel_flag_t with defines. We reached the 32bit limit where does not seem reliable
          to keep using enum.
	* Flags member for ftdm_channel_t is now uint64_t
	* Added FTDM_CHANNEL_CALL_STARTED flag to indicate when the API user knows about a call
	* Refactored raw_data member for ftdm_sigmsg_t. If raw_data needs to be freed it must be requested explicitly
          through the autofree member
	* Added collected member to ftdm_sigmsg_t for FTDM_SIGEVENT_COLLECTED data instead of using raw_data
	* Created define FTDM_DIGITS_LIMIT for DNIS/ANI digits limit
	* Fix some stat checks and outdated code in ftmod_analog
	* Refactored ftdm_channel_get_history_str API to return the time offsets and time since last state change
	* Do not send FTDM_SIGEVENT_STOP and FTDM_SIGEVENT_RELEASED on calls that were never reported to the user

libs/freetdm/src/ftmod/ftmod_analog_em/ftmod_analog_em.c

@@ -467,7 +467,7 @@ static void *ftdm_analog_em_channel_run(ftdm_thread_t *me, void *obj)
 				dtmf_offset = strlen(dtmf);
 				last_digit = elapsed;
 				sig.event_id = FTDM_SIGEVENT_COLLECTED_DIGIT;
-				sig.raw_data = dtmf;
+				ftdm_set_string(sig.ev_data.collected.digits, dtmf);
 				if (ftdm_span_send_signal(ftdmchan->span, &sig) == FTDM_BREAK) {
 					collecting = 0;
 				}