- types_linux.go: Use the kernel-defined termios structure, *not* the
  LIBC-defined one. The LIBC termios structure cannot be safely used
  to do tty-related ioctls on all architectures (e.g. ppc64,
  ppc64le). The kernel termios structure, and the associated
  macros/constants, are defined in: "asm/termbits.h" which is included
  by "linux/termios.h". The LIBC termios structure is defined in
  "bits/termios.h" which is included by "termios.h". These structures
  are *not* the same.

  For systems that have both "struct termios" and "struct termios2"
  use the latter to define the Termios type. This is ok, since the
  "struct termios2" memory layout is compatible with "struct termios"
  (with a couple of fields added at the end). This way, type Termios
  can be used with both: the "old-style" TCSETS[FW], TCGETS ioctls,
  *and* with the new TCSETS[FW]2, TCGETS2 ioctls. The new ioctls allow
  configuring arbitrary baudrates.

  The new Termios definitions (kernel-compatible) have the same fields
  as the old ones (LIBC-derived) so there should be no user-code
  compatibility issues.

Change-Id: I3c1484c60f45b28e13404765c01616c33063afd5
Reviewed-on: https://go-review.googlesource.com/17185Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>