[SoM] ObjC inheritance generates method hiding warnings

[stephen-hawley]

		[Test]
		public void TestCtorJumpInherit ()
		{
			var swiftCode = @"
import Foundation
@objc
open class ImAnNSObject : NSObject {
    public init (nibName: Int, bundle: Int)
    {
        
    }
}

open class MyInheritor : ImAnNSObject {
    public func getValue () -> Int {
        return 17
    }
}
";
			var declID = new CSIdentifier ("cl");
			var decl = CSVariableDeclaration.VarLine (CSSimpleType.Var, declID, new CSFunctionCall ("MyInheritor", true, CSConstant.Val (7), CSConstant.Val (8)));
			var printer = CSFunctionCall.ConsoleWriteLine (new CSFunctionCall ($"{declID.Name}.GetValue", false));
			var callingCode = CSCodeBlock.Create (decl, printer);

			TestRunning.TestAndExecute (swiftCode, callingCode, "17\n", platform: PlatformName.macOS);
		}
	}

The issue appears to be that when the ObjC object is also bound by SoM, it will already have the members in it and we have no idea that we've already bound it and we get a name conflict warning.

Detecting this case is the trick - I can easily detect it when it's within the same module, but if the type came in from an external module that SoM already did the binding for, we can't tell that we had done the binding.