split --filter, nearly ready

[Jim Meyering]

Here's what I have so far.

One remaining task is to write the ChangeLog entry for
Karl's initial change.

[1/8] split: accept new output --filter option
[2/8] split: remove short-named -f option; improve diagnostics
[3/8] split: add tests
[4/8] split: update NEWS
[5/8] split: mark a string for translation
[6/8] strip: style: use braces around 1-stmt-but-multi-line
[7/8] split: don't rely on knowledge that INT_BUFSIZE_BOUND <=
[8/8] doc: document split's new --filter=CMD option

 b/NEWS               |   10 ++
 b/doc/coreutils.texi |   24 +++++
 b/src/split.c        |  211 +++++++++++++++++++++++++++++++++++++++++++++------
 b/tests/Makefile.am  |    1
 b/tests/split/filter |   41 +++++++++
 src/split.c          |   42 ++++++----
 6 files changed, 287 insertions(+), 42 deletions(-)

I've already merged a few small changes into Karl's initial 1/8,
and will merge others (probably 2, 5, 6, 7), but have left them
separate for now to facilitate review.

One oddity that I have not documented is how --elide-empty-files
works with --filter, but I did add a test to demonstrate
the existing behavior:

  # Show how --elide-empty-files works with --filter:
  # split does not run the command (and effectively elides the file)
  # only when the output to that command would have been empty.
  split -e -n 10 --filter='xz > $FILE.xz' /dev/null || fail=1
  stat x?? 2>/dev/null && fail=1

Feedback welcome.