make fcntl module detect O_NOATIME, O_NOFOLLOW on GNU/Linux

[Ben Pfaff]

Without the following, "./gnulib-tool --create-testdir fcntl"
will report
        checking for working fcntl.h... no (bad O_NOATIME, O_NOFOLLOW)
on GNU/Linux, because _GNU_SOURCE is needed to define those
constants.

Anyone object to me pushing this?

commit b9ea9d8163fc97ad8940cfa681a6c4ceb0fc531c
Author: Ben Pfaff <address@hidden>
Date:   Sun Apr 12 16:31:16 2009 -0700

    Make fcntl module detect O_NOATIME, O_NOFOLLOW on GNU/Linux.

diff --git a/ChangeLog b/ChangeLog
index 80aed98..400685b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2009-04-12  Ben Pfaff  <address@hidden>
+
+       Make fcntl module detect O_NOATIME, O_NOFOLLOW on GNU/Linux.
+       * m4/fcntl_h.m4 (gl_FCNTL_H): Require AC_USE_SYSTEM_EXTENSIONS.
+
 2009-03-20  Ben Pfaff  <address@hidden>
 
        Make rename replace existing destinations on Windows.
diff --git a/m4/fcntl_h.m4 b/m4/fcntl_h.m4
index 4a7fc42..f2b09f3 100644
--- a/m4/fcntl_h.m4
+++ b/m4/fcntl_h.m4
@@ -8,6 +8,7 @@ dnl Written by Paul Eggert.
 
 AC_DEFUN([gl_FCNTL_H],
 [
+  AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])
   AC_REQUIRE([gl_FCNTL_H_DEFAULTS])
   AC_CACHE_CHECK([for working fcntl.h], [gl_cv_header_working_fcntl_h],
     [AC_RUN_IFELSE(

-- 
"doe not call up Any that you can not put downe."
--H. P. Lovecraft