[linker] improve method detection in FixAbstractMethodsStep

The forms team run into an issue with debugger in VS [1]. During
investigation it turned out that our FixAbstractMethodsStep injects 2
methods, which were not needed, as the methods were already
implemented. The bug itself looks like an issue, where original mdb
file was used in the apk, instead of the one written by our linker.

This change improves the method detection, where explicit interface
methods name starts with `global::` [2]. In this particular case it
were these methods:

    global::Android.Views.View.IOnTouchListener.OnTouch
    global::Android.Views.View.IOnClickListener.OnClick

This is possibly compiler specific, so we rather look in
MethodDefinition's Overrides to find the interface method and compare
it to the interface method we are looking for.

[1] https://bugzilla.xamarin.com/show_bug.cgi?id=59293
[2] excerpt from ikdasm output:
    .method private hidebysig newslot virtual final
            instance void  'global::Android.Views.View.IOnClickListener.OnClick'(class [Mono.Android]Android.Views.View v) cil managed
    {
      .override [Mono.Android]Android.Views.View/IOnClickListener::OnClick

Author: radekdoulik

src/Xamarin.Android.Build.Tasks/Linker/MonoDroid.Tuner/FixAbstractMethodsStep.cs

@@ -95,8 +95,23 @@ static bool CompareTypes (TypeReference iType, TypeReference tType)
 			return true;
 		}
 
+		bool IsInOverrides (MethodDefinition iMethod, MethodDefinition tMethod)
+		{
+			if (!tMethod.HasOverrides)
+				return false;
+
+			foreach (var o in tMethod.Overrides)
+				if (o != null && iMethod == o.Resolve ())
+					return true;
+
+			return false;
+		}
+
 		bool HaveSameSignature (TypeReference iface, MethodDefinition iMethod, MethodDefinition tMethod)
 		{
+			if (IsInOverrides (iMethod, tMethod))
+				return true;
+
 			if (iMethod.Name != tMethod.Name && (iMethod.DeclaringType == null || (iMethod.DeclaringType.DeclaringType == null ? (string.Format ("{0}.{1}", iface.FullName, iMethod.Name) != tMethod.Name) : (string.Format ("{0}.{1}.{2}", iMethod.DeclaringType.DeclaringType, iface.Name, iMethod.Name) != tMethod.Name))))
 				return false;
 

tests/CodeGen-Binding/Xamarin.Android.FixJavaAbstractMethod-APIv1Binding/java/test/bindings/Cursor.java

@@ -3,6 +3,7 @@
 public interface Cursor {
     void method();
     int methodWithRT ();
+    int methodWithCursor (Cursor cursor);
     int methodWithParams (int number, String text);
     int methodWithParams (int number, String text, float real);
 }

tests/CodeGen-Binding/Xamarin.Android.FixJavaAbstractMethod-APIv2Binding/java/test/bindings/Cursor.java

@@ -5,6 +5,7 @@ public interface Cursor {
     void newMethod();
     int methodWithRT ();
     int newMethodWithRT ();
+    int methodWithCursor (Cursor cursor);
     int methodWithParams (int number, String text);
     int newMethodWithParams (int number, String text);
     int methodWithParams (int number, String text, float real);

tests/CodeGen-Binding/Xamarin.Android.FixJavaAbstractMethod-Library/MyClrCursor.cs

@@ -3,7 +3,7 @@
 
 namespace Library
 {
-	public class MyClrCursor : Java.Lang.Object, ICursor
+	public class MyClrCursor : Java.Lang.Object, global::Test.Bindings.ICursor
 	{
 		public void Method ()
 		{
@@ -23,6 +23,11 @@ public int MethodWithRT ()
 		{
 			return 3;
 		}
+
+		int global::Test.Bindings.ICursor.MethodWithCursor (global::Test.Bindings.ICursor cursor)
+		{
+			return 4;
+		}
 	}
 }
 

tests/CodeGen-Binding/Xamarin.Android.JcwGen-Tests/BindingTests.cs

@@ -179,6 +179,11 @@ public void JavaAbstractMethodTest ()
 				if (e.GetType ().ToString () != "Java.Lang.AbstractMethodError")
 					throw e;
 			}
+
+			var mi = ic.GetType ().GetMethod ("MethodWithCursor");
+			var mi2 = ic.GetType ().GetMethod ("global::Test.Bindings.ICursor.MethodWithCursor");
+			if (!(mi == mi2))
+				throw new Exception ("FixAbstractMethodStep broken, MethodWithRT added, while it should not be");
 		}
 
 		// Context https://bugzilla.xamarin.com/show_bug.cgi?id=36036