3djc/fix #3965 (#3981)

* Introduce 'magnetic 0' for trims

* Removing magnetic 0 that could feel unnatural to a force to 0 when changing side

* Efficiency

* Optimise

* Optimise (reverted from commit 41fc09f0bd37dd4c3067f7406562ab68c07b22ca)

* Bertrand's feedback incorporated

* Another one (bites the dust ?)

radio/src/opentx.cpp

@@ -1300,7 +1300,8 @@ uint8_t checkTrim(event_t event)
     int16_t after = (k&1) ? before + v : before - v;   // positive = k&1
     bool beepTrim = false;
 
-    if (!thro && after==0 && before!=0) {
+    if (!thro && ((after < 0) != (before < 0)) && before!=0) { //forcing a stop at centerered trim when changing sides
+      after = 0;
       beepTrim = true;
       AUDIO_TRIM_MIDDLE();
       pauseEvents(event);