Fix #2505: Do treat whole resource name as file name without directory at the start of GetFileNameForResource.

ICSharpCode.Decompiler/CSharp/ProjectDecompiler/WholeProjectDecompiler.cs

@@ -369,7 +369,7 @@ namespace ICSharpCode.Decompiler.CSharp.ProjectDecompiler
 			// the directory part Namespace1\Namespace2\... reuses as many existing directories as
 			// possible, and only the remaining name parts are used as prefix for the filename.
 			string[] splitName = fullName.Split(Path.DirectorySeparatorChar);
-			string fileName = fullName;
+			string fileName = string.Join(".", splitName);
 			string separator = Path.DirectorySeparatorChar.ToString();
 			for (int i = splitName.Length - 1; i > 0; i--)
 			{