bug: Include <stdbool.h>

We have #define BUG() BUG_ON(true) here, where 'true'
is defined in stdbool header, so to be able to include
bug.h on its own -- include needed header inplace.
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

include/bug.h

@@ -2,6 +2,7 @@
 #define __CR_BUG_H__
 
 #include <signal.h>
+#include <stdbool.h>
 
 #include "compiler.h"
 #include "log.h"