[mutter] Don't re-define auto cleanup symbols

[Emmanuele Bassi <ebassi src gnome org>]

commit aeda556af1fa8abfac0d0856f6bc03f86ab69409
Author: Emmanuele Bassi <ebassi gnome org>
Date:   Tue May 3 07:54:42 2016 +0100

    Don't re-define auto cleanup symbols
    
    Starting from GLib 2.49, the gdbus-codegen tool automatically generates
    the auto cleanup symbols for the GDBus proxy and skeleton interfaces.
    
    Since we don't depend on a specific version of GLib we need to
    conditionally generate the auto cleanup symbols in case an older version
    of gdbus-codegen is used when building Mutter.
    
    This commit unbreaks the build under GNOME Continuous, which has been
    failing with:
    
    usr/include/glib-2.0/glib/gmacros.h:415:43: error: redefinition of 'glib_autoptr_cleanup_Login1Session'
     #define _GLIB_AUTOPTR_FUNC_NAME(TypeName) glib_autoptr_cleanup_##TypeName
                                               ^
    [...]
    /usr/include/glib-2.0/glib/gmacros.h:415:43: note: previous definition of 
'glib_autoptr_cleanup_Login1Session' was here
    ./meta-dbus-login1.h:82:1: note: in expansion of macro 'G_DEFINE_AUTOPTR_CLEANUP_FUNC'
     G_DEFINE_AUTOPTR_CLEANUP_FUNC (Login1Session, g_object_unref)
     ^

 src/backends/native/meta-launcher.c |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)
---
diff --git a/src/backends/native/meta-launcher.c b/src/backends/native/meta-launcher.c
index 824f918..2a7b279 100644
--- a/src/backends/native/meta-launcher.c
+++ b/src/backends/native/meta-launcher.c
@@ -49,8 +49,13 @@
 G_DEFINE_AUTOPTR_CLEANUP_FUNC(GUdevDevice, g_object_unref)
 G_DEFINE_AUTOPTR_CLEANUP_FUNC(GUdevClient, g_object_unref)
 G_DEFINE_AUTOPTR_CLEANUP_FUNC(GUdevEnumerator, g_object_unref)
+
+#ifndef glib_autoptr_cleanup_Login1Session
 G_DEFINE_AUTOPTR_CLEANUP_FUNC(Login1Session, g_object_unref)
+#endif
+#ifndef glib_autoptr_cleanup_Login1Seat
 G_DEFINE_AUTOPTR_CLEANUP_FUNC(Login1Seat, g_object_unref)
+#endif
 
 struct _MetaLauncher
 {