Third attempt: Improve how TimerDemo.c manages differences between the tick count and its own internal tick count, which can temporarily differ when the tick hook is called while the scheduler is suspended.

FreeRTOS/Demo/Common/Minimal/TimerDemo.c

@@ -737,9 +737,9 @@ static portTickType uxTick = ( portTickType ) -1;
 	will expire when the kernel's tick count is (100 + xBasePeriod).  For this
 	reason xMargin is used as an allowable margin for premature timer expiries
 	as well as late timer expiries. */
-	const portTickType xMargin = 5;
+	const portTickType xMargin = 6;
 #else
-	const portTickType xMargin = 2;
+	const portTickType xMargin = 3;
 #endif