Bug#215404: di_check_dir() missing

[Petter Reinholdtsen <pere@hungry.com>]

[Richard Hirst]
> debug builds of kbd-chooser call di_check_dir() but versions of
> libdebian-installer beyond 0.15 do not provide it.

Checking d-i/doc/libdi-changes.txt, I do not find that function
mentioned at all.  I'm not sure what happened to it, nor why it was
removed.

Perhaps kbd-chooser should be changed instead of libd-i?  The function
is used in quite a few places in kbd-chooser:

  at-kbd.c:     assert (di_check_dir ("/proc") == 1);
  at-kbd.c:     if (di_check_dir ("/proc/bus/input") >= 0) {
  usb-kbd.c:    if (di_check_dir ("/proc/bus/input") >= 0) { // 2.6 kernel
  acorn-kbd.c:  assert (di_check_dir ("/proc") == 1);
  acorn-kbd.c:  if (di_check_dir ("/proc/bus/input") >= 0) {
  amiga-kbd.c:  assert (di_check_dir ("/proc") == 1);
  amiga-kbd.c:  if (di_check_dir ("/proc/bus/input") >= 0) {
  mac-kbd.c:    if (di_check_dir ("/proc/bus/input") >= 0) {
  sparc-kbd.c:    assert (di_check_dir ("/proc") == 1);
  sparc-kbd.c:    if (di_check_dir ("/proc/bus/input") >= 0) {