[introspection] Fix a few issues found on iPad Air 2 with iOS 12.

tests/introspection/ApiSelectorTest.cs

@@ -583,6 +583,15 @@ protected virtual bool Skip (Type type, string selectorName)
 					return true;
 				}
 				break;
+			case "MPSCnnBinaryKernel":
+				switch (selectorName) {
+				// Xcode 9.4 removed both selectors from MPSCnnBinaryKernel, reported radar https://trello.com/c/7EAM0qk1
+				// but apple says this was intentional.
+				case "kernelHeight":
+				case "kernelWidth":
+					return true;
+				}
+				break;
 			}
 
 			// old binding mistake

tests/introspection/Mac/MacApiSelectorTest.cs

@@ -200,15 +200,6 @@ protected override bool Skip (Type type, string selectorName)
 			case "readingOptionsForType:pasteboard:":
 			case "writingOptionsForType:pasteboard:":
 				return true; // Optional selectors on NSPasteboardReading/NSPasteboardWriting
-			// Xcode 9.4 removed both selectors from MPSCnnBinaryKernel, reported radar https://trello.com/c/7EAM0qk1
-			// but apple says this was intentional.
-			case "kernelHeight":
-			case "kernelWidth":
-				switch (type.Name) {
-				case "MPSCnnBinaryKernel":
-					return true;
-				}
-				break;
 			case "newWindowForTab:": // "This method can be implemented in the responder chain", optional but not protocol directly on NSResponder
 				switch (type.Name) {
 				case "NSViewController":

tests/introspection/iOS/iOSApiCtorInitTest.cs

@@ -73,7 +73,10 @@ protected override bool Skip (Type type)
 					return true;
 				break;
 #endif // !__WATCHOS__
-			case "CoreNFC": // Only available on device
+			case "CoreNFC": // Only available on devices that support NFC, so check if NFCNDEFReaderSession is present.
+				if (Class.GetHandle ("NFCNDEFReaderSession") == IntPtr.Zero)
+					return true;
+				break;
 			case "DeviceCheck": // Only available on device
 				if (Runtime.Arch == Arch.SIMULATOR)
 					return true;

tests/introspection/iOS/iOSApiFieldTest.cs

@@ -53,7 +53,10 @@ protected override bool Skip (PropertyInfo p)
 			case "MonoTouch.MetalKit":
 			case "MetalPerformanceShaders":
 			case "MonoTouch.MetalPerformanceShaders":
-			case "CoreNFC": // Only available on device
+			case "CoreNFC": // Only available on devices that support NFC, so check if NFCNDEFReaderSession is present.
+				if (Class.GetHandle ("NFCNDEFReaderSession") == IntPtr.Zero)
+					return true;
+				break;
 			case "DeviceCheck": // Only available on device
 				if (Runtime.Arch == Arch.SIMULATOR)
 					return true;
@@ -108,6 +111,10 @@ protected override bool Skip (PropertyInfo p)
 		protected override bool Skip (string constantName, string libraryName)
 		{
 			switch (libraryName) {
+			case "CoreNFC": // Only available on devices that support NFC, so check if NFCNDEFReaderSession is present.
+				if (Class.GetHandle ("NFCNDEFReaderSession") == IntPtr.Zero)
+					return true;
+				break;
 			case "IOSurface":
 				return Runtime.Arch == Arch.SIMULATOR && !TestRuntime.CheckXcodeVersion (9, 0);
 			}
@@ -141,7 +148,6 @@ protected override bool Skip (string constantName, string libraryName)
 			case "MTKTextureLoaderOptionTextureCPUCacheMode":
 			case "MTKModelErrorDomain":
 			case "MTKModelErrorKey":
-			case "NFCISO15693TagResponseErrorKey": // Not in simulator since no NFC on it
 				return Runtime.Arch == Arch.SIMULATOR;
 			default:
 				return false;

tests/introspection/iOS/iOSApiProtocolTest.cs

@@ -46,6 +46,10 @@ protected override bool Skip (Type type)
 				if (Runtime.Arch == Arch.SIMULATOR)
 					return true;
 				break;
+			case "CoreNFC": // Only available on devices that support NFC, so check if NFCNDEFReaderSession is present.
+				if (Class.GetHandle ("NFCNDEFReaderSession") == IntPtr.Zero)
+					return true;
+				break;
 			}
 
 			switch (type.Name) {

tests/introspection/iOS/iOSApiSelectorTest.cs

@@ -62,7 +62,10 @@ protected override bool Skip (Type type)
 					return true;
 				break;
 			// Xcode 9
-			case "CoreNFC":
+			case "CoreNFC": // Only available on devices that support NFC, so check if NFCNDEFReaderSession is present.
+				if (Class.GetHandle ("NFCNDEFReaderSession") == IntPtr.Zero)
+					return true;
+				break;
 			case "DeviceCheck":
 				if (Runtime.Arch == Arch.SIMULATOR)
 					return true;