SoftwareTimerSupervisor::tickInterruptHandler(): improve implementation
SoftwareTimerSupervisor::tickInterruptHandler(): improve implementation

"Unlink" the item that is currently processed before calling its run()
function. This way the function can restart (and re-queue) the timer,
which was not possible in previous implementation.
CezaryGapinski/distortos,jasmin-j/distortos,jasmin-j/distortos,DISTORTEC/distortos,jasmin-j/distortos,CezaryGapinski/distortos,CezaryGapinski/distortos,DISTORTEC/distortos,CezaryGapinski/distortos,DISTORTEC/distortos,jasmin-j/distortos,jasmin-j/distortos,DISTORTEC/distortos,CezaryGapinski/distortos