libstb/container: Add missing includes
libstb will sometimes randomly fail to compile due to missing types.
This appears to solve it but I didn't look too far into why it mostly
works (or can be made to work with make clean) without this.
#define __STB_CONTAINER_H
#include <stdint.h>
+#include <stdbool.h>
#include <stdlib.h>
+#include <ccan/short_types/short_types.h>
#include <ccan/endian/endian.h>
#define SECURE_BOOT_HEADERS_SIZE 4096
