Fixes #2009: Timer Voice minute call not working for persistent timers

Timers moved to timer.cpp
Added timer overflow protection
Added timer gtests
THt mode now triggers on THR>10%

radio/src/mixer.cpp

@@ -35,6 +35,7 @@
  */
 
 #include "opentx.h"
+#include "timers.h"
 
 #if defined(PCBTARANIS)
   int8_t  virtualInputsTrims[NUM_INPUTS];