ivi-shell-user-interface: fix runtime error caused by missing header inclusion

when weston is running on qemux86 device, there is an error with following.

[08:02:07.897] launching '/usr/lib/weston/weston-ivi-shell-user-interface'
[08:02:08.201] /usr/lib/weston/weston-ivi-shell-user-interface died on signal 11

this is caused by type mismatch, and
it does occur on qemux86-64

Signed-off-by: Yong-iL Joh <yong-il.joh@windriver.com>
Acked-by: Daniel Stone <daniel@fooishbar.org>
Reviewed-by: Bryce Harrington <bryce@osg.samsung.com>

clients/ivi-shell-user-interface.c

@@ -21,6 +21,8 @@
  * DEALINGS IN THE SOFTWARE.
  */
 
+#include "config.h"
+
 #include <sys/wait.h>
 #include <unistd.h>
 #include <stdlib.h>