TIOCSIG is linux specific, so include the linux ioctl header to make sure
it's defined. We currently rely on some rather non-obvious recursive
includes. Make sure its always defined regardless of the system headers.
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
+#include <linux/ioctl.h>
#include <pty.h>
#include <signal.h>
#include <stdbool.h>
#include <pty.h>
#include <signal.h>
#include <stdbool.h>