Handle locales with the same daylight savings time start and end

If the first and second transition DateTime objects are the same,
`ValidateAdjustmentRule` will throw an exception. I'm unsure why these
would be the same, but we do see that occur for some locales. In that
case, just exit early.

This change corrects Unity case 1160695.

mcs/class/corlib/System/TimeZoneInfo.Unity.cs

@@ -54,6 +54,12 @@ static List<AdjustmentRule> CreateAdjustmentRule (int year, out Int64[] data, ou
 			if(daylightNameCurrentYear != names[(int)TimeZoneNames.DaylightNameIdx])
 				return rulesForYear;
 
+			// If the first and second transition DateTime objects are the same, ValidateAdjustmentRule will throw
+			// an exception. I'm unsure why these would be the same, but we do see that occur for some locales.
+			// In that case, just exit early.
+			if (firstTransition.Equals(secondTransition))
+				return rulesForYear;
+
 			var beginningOfYear = new DateTime (year, 1, 1, 0, 0, 0, 0);
 			var endOfYearDay = new DateTime (year, 12, DateTime.DaysInMonth (year, 12));
 			var endOfYearMaxTimeout = new DateTime (year, 12, DateTime.DaysInMonth(year, 12), 23, 59, 59, 999);