[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 method name starts
with `global::`. In this particular case it were these methods:

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

[1] https://bugzilla.xamarin.com/show_bug.cgi?id=59293

Author: radekdoulik

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

@@ -97,7 +97,12 @@ static bool CompareTypes (TypeReference iType, TypeReference tType)
 
 		bool HaveSameSignature (TypeReference iface, MethodDefinition iMethod, MethodDefinition tMethod)
 		{
-			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))))
+			var tName = tMethod.Name.StartsWith ("global::") ? tMethod.Name.Substring (8) : tMethod.Name;
+			if (iMethod.Name != tName
+			    && (iMethod.DeclaringType == null
+			        || (iMethod.DeclaringType.DeclaringType == null
+			            ? (string.Format ("{0}.{1}", iface.FullName, iMethod.Name) != tName)
+			            : (string.Format ("{0}.{1}.{2}", iMethod.DeclaringType.DeclaringType, iface.Name, iMethod.Name) != tName))))
 				return false;
 
 			if (!CompareTypes (iMethod.MethodReturnType.ReturnType, tMethod.MethodReturnType.ReturnType))