new getopt features committed

new getopt features committed

[Rich Felker]

I've just committed support for options after non-option arguments
("argv permutation" ala GNU getopt) in getopt_long only (same way it
works on BSD -- plain getopt is always POSIX conforming but
getopt_long has the new feature) and abbreviated long options.
Hopefully this eliminates the need to patch libc (like Alpine is doing
up til now) or individual apps (like some other dists are doing) with
an alternate getopt implementation.

A couple differences from GNU and BSD variants:

- The code in musl now does not honor $POSIXLY_CORRECT. The only way
  to suppress argv permutation in getopt_long is with a leading '+' in
  the optstring. This may be changed depending on feedback.

- The progression of optind is different, and IMO much less
  counter-intuitive, when options after non-option arguments are being
  processed. But the final argv[] order and final optind after
  getopt_long returns -1 should be the same.

- No additional internal state is kept for non-option argument
  skipping. As a result, more passes over argv[] are needed in some
  cases, but it shouldn't make a practical performance difference.

- Reporting of errors may be different; this is unintentional and
  should be fixed. In particular getopt_long does not print any
  messages for long option errors; only short options (handled by
  getopt internally) produce messages. Return values may be different
  too.

If there are any regressions, let me know.

Rich