Don't ignore method-less types when scanning

They might contain nested types with interesting methods.

Doh.

Author: grendello

src/Xamarin.Android.Build.Tasks/Utilities/PinvokeScanner.cs

@@ -67,6 +67,12 @@ void Scan (AndroidTargetArch targetArch, AssemblyDefinition assembly, HashSet<st
 
 	void Scan (AndroidTargetArch targetArch, TypeDefinition type, HashSet<string> pinvokeCache, List<PinvokeEntryInfo> pinvokes)
 	{
+		if (type.HasNestedTypes) {
+			foreach (TypeDefinition nestedType in type.NestedTypes) {
+				Scan (targetArch, nestedType, pinvokeCache, pinvokes);
+			}
+		}
+
 		if (!type.HasMethods) {
 			return;
 		}
@@ -87,13 +93,5 @@ void Scan (AndroidTargetArch targetArch, TypeDefinition type, HashSet<string> pi
 			pinvokeCache.Add (key);
 			pinvokes.Add (pinfo);
 		}
-
-		if (!type.HasNestedTypes) {
-			return;
-		}
-
-		foreach (TypeDefinition nestedType in type.NestedTypes) {
-			Scan (targetArch, nestedType, pinvokeCache, pinvokes);
-		}
 	}
 }