Append termio.h.
* Makefile ($(includedir)/stubs.h): Print a msg if we do nothing.
* misc/sgtty.h: Add forward decl of struct sgttyb in case it is never
defined.
* sysdeps/unix/sysv/linux/termio.h: New file.
* sysdeps/unix/sysv/linux/Dist: Add it.
* sysdeps/unix/sysv/linux/ioctl-types.h: New file, wrapper around
kernel header <asm/termios.h>.
* misc/Makefile (headers): Add ioctl-types.h.
* sysdeps/generic/ioctl-types.h: New file.
* misc/sys/ioctl.h: Include <ioctl-types.h>.
(struct tchars, struct ltchars, struct sgttyb, struct winsize,
struct ttysize): Types moved there.
