minor fixes and cleanups

- new delay concept for aprsis to rf / kiss to rf / serial tnc to rf
    -> prevents flooding rf channel

- work on code handling variable nextTX (fix cleanup).
  - Course-change.detection ignored on high speed:
    During review of my code I saw if nextTX was set to 1 due to course change,
    it was re-set in the next tests below to sb_min_intervali. if current speed
    was >= sb_max_speed.
  - if we TXed in the last round and have in this round detected a course
    change, we don't TX this round; we now remember that condition for the next
    rounds until 5-20s time has passed):
      if (tmp_t_since_last_sb_tx >= (6000000L / lora_speed) && (lastPositionTX + nextTX) < millis())
        ..

Signed-off-by: Thomas Osterried <dl9sau@darc.de>

src/TTGO_T-Beam_LoRa_APRS.ino

@@ -7389,9 +7389,9 @@ invalid_packet:
 
   boolean display_was_updated = false;
   ulong tmp_t_since_last_sb_tx = millis() - lastPositionTX;
-  static boolean reason_course_change = 0;  // used as hint for sendpacket. static, because
-                                            // we may not be sure (if we are not TXing now but in one of the next rounds)
-                                            // when looking at nextTX == 0: was  the reason a course change
+  static boolean reason_course_change = false;  // used as hint for sendpacket. static, because
+                                                // we may not be sure (if we are not TXing now but in one of the next rounds)
+                                                // when looking at nextTX == 0: was  the reason a course change
 
   // Send position, if not requested to do not ;) But enter this part if user likes our LA/LON/SPD/CRS to be displayed on his screen ('!gps_allow_sleep_while_kiss' caused 'gps_state false')
   if (!gps_state && (!dont_send_own_position_packets || !(lora_tx_enabled || aprsis_enabled)))
@@ -7507,7 +7507,7 @@ invalid_packet:
         writedisplaytext("  ((TX))","",OledLine2,OledLine3,OledLine4,OledLine5);
       }
       sendpacket(SP_POS_GPS | (reason_course_change ? SP_ENFORCE_COURSE : 0 ));
-      reason_course_change = 0;
+      reason_course_change = false;
       // for fixed beacon (if we loose gps fix, we'll send our last position in fix_beacon_interval)
       // We just transmitted. We transmitted due to turn (nextTX == 1)? Also Don't TX again in next round, sendpacket() adjustet nextTX
     } else {