Fix building against old glib versions

We need to include libglnx.h in places where ostree-autocleanups.h is
included, so that we get backports of G_DEFINE_AUTOPTR_CLEANUP_FUNC and
friends.

Closes: #1615
Approved by: jlebon

src/libostree/ostree-repo-finder-avahi-parser.c

@@ -29,6 +29,7 @@
 #include <avahi-common/strlst.h>
 #include <glib.h>
 #include <glib-object.h>
+#include <libglnx.h>
 #include <string.h>
 
 #include "ostree-autocleanups.h"

src/libostree/ostree-repo-finder-avahi.c

@@ -43,6 +43,7 @@
 #include <gio/gio.h>
 #include <glib.h>
 #include <glib-object.h>
+#include <libglnx.h>
 
 #include "ostree-autocleanups.h"
 #include "ostree-repo-finder.h"

src/libostree/ostree-repo-finder.c

@@ -27,6 +27,7 @@
 #include <gio/gio.h>
 #include <glib.h>
 #include <glib-object.h>
+#include <libglnx.h>
 
 #include "ostree-autocleanups.h"
 #include "ostree-core.h"

tests/repo-finder-mount.c

@@ -27,6 +27,7 @@
 #include <gio/gio.h>
 #include <glib.h>
 #include <glib-object.h>
+#include <libglnx.h>
 #include <locale.h>
 
 #include "ostree-autocleanups.h"