Extract wxPipeInputStream and wxPipeOutputStream in a header.

No real changes, just put these classes in a private header. They're still not
part of the public API but at least it will be easier to reuse them inside the
library itself in the upcoming commits.

See #10258.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@74336 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/private/pipestream.h

@@ -0,0 +1,30 @@
+///////////////////////////////////////////////////////////////////////////////
+// Name:        wx/private/pipestream.h
+// Purpose:     Declares wxPipeInputStream and wxPipeOutputStream.
+// Author:      Vadim Zeitlin
+// Modified by: Rob Bresalier
+// Created:     2013-04-27
+// RCS-ID:      $Id$
+// Copyright:   (c) 2003 Vadim Zeitlin <vadim@wxwidgets.org>
+//              (c) 2013 Rob Bresalier
+// Licence:     wxWindows licence
+///////////////////////////////////////////////////////////////////////////////
+
+#ifndef _WX_PRIVATE_PIPESTREAM_H_
+#define _WX_PRIVATE_PIPESTREAM_H_
+
+#include "wx/platform.h"
+
+// wxPipeInputStream is a platform-dependent input stream class (i.e. deriving,
+// possible indirectly, from wxInputStream) for reading from a pipe, i.e. a
+// pipe FD under Unix or a pipe HANDLE under MSW. It provides a single extra
+// IsOpened() method.
+//
+// wxPipeOutputStream is similar but has no additional methods at all.
+#ifdef __UNIX__
+    #include "wx/unix/private/pipestream.h"
+#elif defined(__WINDOWS__) && !defined(__WXWINCE__)
+    #include "wx/msw/private/pipestream.h"
+#endif
+
+#endif // _WX_PRIVATE_PIPESTREAM_H_