[gtk+] configure: Move AC_USE_SYSTEM_EXTENSIONS up

[Benjamin Otte <otte src gnome org>]

commit f1b14a33b56d49470dbb736fe9cca20c52948a1b
Author: Benjamin Otte <otte redhat com>
Date:   Wed Aug 27 21:24:27 2014 +0200

    configure: Move AC_USE_SYSTEM_EXTENSIONS up
    
    We don't want to get warnings from autoconf about
    AC_USE_SYSTEM_EXTENSIONS coming after AC_COMPILE_IFELSE.

 configure.ac |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 31228ca..6b7ddbe 100644
--- a/configure.ac
+++ b/configure.ac
@@ -189,6 +189,9 @@ case $host in
     ;;
 esac
 
+# Define _GNU_SOURCE etc. where appropriate, e.g. for strptime() on glibc
+AC_USE_SYSTEM_EXTENSIONS
+
 dnl
 dnl Check for a working C++ compiler, but do not bail out, if none is found.
 dnl We use this for an automated test for C++ header correctness.
@@ -227,8 +230,6 @@ LT_INIT([disable-static win32-dll])
 # Create libtool early, because it's used in configure
 LT_OUTPUT
 
-# Define _GNU_SOURCE etc. where appropriate, e.g. for strptime() on glibc
-AC_USE_SYSTEM_EXTENSIONS
 # Make sure we use 64-bit versions of various file stuff.
 AC_SYS_LARGEFILE