Import new gnulib.

m4/glibc2.m4

@@ -1,5 +1,6 @@
-# glibc2.m4 serial 2
-dnl Copyright (C) 2000-2002, 2004, 2008-2010 Free Software Foundation, Inc.
+# glibc2.m4 serial 3
+dnl Copyright (C) 2000-2002, 2004, 2008, 2010-2013 Free Software Foundation,
+dnl Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
 dnl with or without modifications, as long as this notice is preserved.
@@ -15,7 +16,7 @@ AC_DEFUN([gt_GLIBC2],
         [
 #include <features.h>
 #ifdef __GNU_LIBRARY__
- #if (__GLIBC__ >= 2)
+ #if (__GLIBC__ >= 2) && !defined __UCLIBC__
   Lucky GNU user
  #endif
 #endif