Fix a segfault in get_contents

We would set the last element of the buffer to zero, just to be sure,
but wouldn't allocate that much memory, thus getting a segfault.

c/ton/main.c

		goto err;
	}
	char *buf = malloc(f_stat.st_size);
	char *buf = malloc(f_stat.st_size + 1);
	memset(buf, 0, f_stat.st_size);
	fread(buf, f_stat.st_size, 1, f);
	buf[f_stat.st_size] = '\0';