Add paragraph about IO::Path subclasses

Author: lizmat

S32-setting-library/IO.pod

@@ -24,8 +24,8 @@ Synopsis 32: Setting Library - IO
 
     Created: 19 Feb 2009
 
-    Last Modified: 23 Sep 2014
-    Version: 24
+    Last Modified: 29 Sep 2014
+    Version: 25
 
 =head1 Overview
 
@@ -1055,6 +1055,16 @@ rather than words themselves.  By default, words will be returned.
 
 =back
 
+=head3 Subclasses
+
+The C<IO::Path> class may have C<IO::Spec> specific subclasses.  But basically,
+these would only implicitely specify the C<IO::Class> to be specified for
+the C<.new> method:
+
+  class IO::Path::Win32 {
+      method new(|c) { IO::Path.new(|c, :SPEC(IO::Spec::Win32) }
+  }
+
 =head2 IO::Handle
 
     class IO::Handle does IO { ... }