[EventKit] Fix a few issues found with iOS 11 (#2198)

* [EventKit] Obsolete the EKAlarm constructor and update tests.

Apple's documentation says "Use the alarmWithAbsoluteDate: and
alarmWithRelativeOffset: class methods to create an alarm", and additionally
calling the default constructor crashes, so obsolete the constructor and don't
call it from tests either.

* [EventKit] Make EKCalendarItem abstract according to Apple's documentation.

Since EKCalendarItem is an abstract class, tests should obviously not create
instances of it - and in fact it fails:

    [FAIL] CalendarItemTest.NullAllowedTest : Foundation.MonoTouchException : Objective-C exception thrown. Name: NSInvalidArgumentException Reason: +[EKCalendarItem frozenClass]: unrecognized selector sent to class 0x10e02bfa0

* [tests] Remove removed file from xammac tests as well.

src/EventKit/EventKit.cs

@@ -72,6 +72,13 @@ namespace XamCore.EventKit {
 			get { throw new NotSupportedException (); }
 			set { throw new NotSupportedException (); }
 		}
+#endif
+	}
+
+	partial class EKAlarm {
+#if !XAMCORE_4_0
+		[Obsolete ("Use the static methods FromDate or FromTimeInterval to create alarms")]
+		public EKAlarm () {}
 #endif
 	}
 }

src/eventkit.cs

@@ -54,6 +54,9 @@ namespace XamCore.EventKit {
 	[Since (5,0)]
 	[Mac (10,8, onlyOn64: true)]
 	[BaseType (typeof (EKObject))]
+#if XAMCORE_4_0	
+	[Abstract] // "The EKCalendarItem class is a an abstract superclass ..." from Apple docs.
+#endif
 	interface EKCalendarItem {
 #if !MONOMAC
 		// Never made avaialble on MonoMac
@@ -188,6 +191,7 @@ namespace XamCore.EventKit {
 	[Since (4,0)]
 	[Mac (10,8, onlyOn64: true)]
 	[BaseType (typeof (EKObject))]
+	[DisableDefaultCtor] // Documentation says to use the static methods FromDate/FromTimeInterval to create instances
 	interface EKAlarm : NSCopying {
 		[Export ("relativeOffset")]
 		double RelativeOffset { get; set;  }

tests/monotouch-test/EventKit/AlarmTest.cs

@@ -33,7 +33,7 @@ namespace MonoTouchFixtures.EventKit {
 		[Test]
 		public void NullAllowedTest ()
 		{
-			using (var alarm = new EKAlarm ()) {
+			using (var alarm = EKAlarm.FromTimeInterval (1234)) {
 				alarm.AbsoluteDate = null;
 				alarm.StructuredLocation = null;
 			}

tests/monotouch-test/EventKit/CalendarItemTest.cs

@@ -1,43 +0,0 @@
-//
-// Unit tests for EKCalendarItem
-//
-// Authors:
-//	Rolf Bjarne Kvinge <rolf@xamarin.com>
-//
-// Copyright 2013 Xamarin Inc. All rights reserved.
-//
-
-#if !__TVOS__
-
-using System;
-#if XAMCORE_2_0
-using Foundation;
-using CoreGraphics;
-using EventKit;
-using ObjCRuntime;
-#else
-using MonoTouch.CoreGraphics;
-using MonoTouch.EventKit;
-using MonoTouch.Foundation;
-using MonoTouch.ObjCRuntime;
-using MonoTouch.UIKit;
-#endif
-using NUnit.Framework;
-
-namespace MonoTouchFixtures.EventKit {
-	
-	[TestFixture]
-	[Preserve (AllMembers = true)]
-	public class CalendarItemTest {
-
-		[Test]
-		public void NullAllowedTest ()
-		{
-			using (var item = new EKCalendarItem ()) {
-				item.Notes = null;
-			}
-		}
-	}
-}
-
-#endif // !__TVOS__

tests/monotouch-test/monotouch-test.csproj

@@ -349,7 +349,6 @@
     <Compile Include="MapKit\LocalSearchTest.cs" />
     <Compile Include="MapKit\LocalSearchRequestTest.cs" />
     <Compile Include="Foundation\CalendarTest.cs" />
-    <Compile Include="EventKit\CalendarItemTest.cs" />
     <Compile Include="EventKit\AlarmTest.cs" />
     <Compile Include="CoreGraphics\ContextTest.cs" />
     <Compile Include="CoreGraphics\DataConsumerTest.cs" />

tests/xammac_tests/xammac_tests.csproj

@@ -584,9 +584,6 @@
     <Compile Include="..\monotouch-test\EventKit\AlarmTest.cs">
       <Link>EventKit\AlarmTest.cs</Link>
     </Compile>
-    <Compile Include="..\monotouch-test\EventKit\CalendarItemTest.cs">
-      <Link>EventKit\CalendarItemTest.cs</Link>
-    </Compile>
     <Compile Include="..\monotouch-test\EventKit\CalendarTest.cs">
       <Link>EventKit\CalendarTest.cs</Link>
     </Compile>