threadlib: avoid warning

[Bruno Haible]

This avoids a warning from the C compiler on OSF/1 5.1:
  cc: Warning: ./threadlib.c, line 70: Source file does not contain any 
declarations.


2009-01-25  Bruno Haible  <address@hidden>

        * lib/glthread/threadlib.c (dummy): New declaration.

--- lib/glthread/threadlib.c.orig       2009-01-25 23:29:06.000000000 +0100
+++ lib/glthread/threadlib.c    2009-01-25 23:28:37.000000000 +0100
@@ -1,5 +1,5 @@
 /* Multithreading primitives.
-   Copyright (C) 2005-2008 Free Software Foundation, Inc.
+   Copyright (C) 2005-2009 Free Software Foundation, Inc.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -67,3 +67,7 @@
 #endif
 
 /* ========================================================================= */
+
+/* This declaration is solely to ensure that after preprocessing
+   this file is never empty.  */
+typedef int dummy;