[generator] fix bogus type name in warnings for duplicate fields. (dotnet#191)

It had annoyed me by reporting warnings on android.app.Notification.Action
as "Android.App.Action", which doesn't exist. It was due to careless use of
GenBase.Name combined with GenBase.Namespace which never cared about nested
types.

Author: atsushieno

tools/generator/GenBase.cs

@@ -565,11 +565,11 @@ public bool GenFields (StreamWriter sw, string indent, CodeGenerationOptions opt
 			bool needsProperty = false;
 			foreach (Field f in fields) {
 				if (ContainsName (f.Name)) {
-					Report.Warning (0, Report.WarningFieldNameCollision, "Skipping {0}.{1}.{2}, due to a duplicate field, method or nested type name.", this.Namespace, this.Name, f.Name);
+					Report.Warning (0, Report.WarningFieldNameCollision, "Skipping {0}.{1}, due to a duplicate field, method or nested type name. {2} (Java type: {3})", this.FullName, f.Name, HasNestedType (f.Name) ? "(Nested type)" : ContainsProperty (f.Name, false) ? "(Property)" : "(Method)", this.JavaName);
 					continue;
 				}
 				if (seen != null && seen.Contains (f.Name)) {
-					Report.Warning (0, Report.WarningDuplicateField, "Skipping {0}.{1}.{2}, due to a duplicate field.", this.Namespace, this.Name, f.Name);
+					Report.Warning (0, Report.WarningDuplicateField, "Skipping {0}.{1}, due to a duplicate field. (Field) (Java type: {2})", this.FullName, f.Name, this.JavaName);
 					continue;
 				}
 				if (f.Validate (opt, TypeParameters)) {