minor, conditionalise pseudo-tty support on HAVE_PTY_H

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
chore, actually check for pty.h

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
minor, generate a stub getopt.h when none can be found during configure time

POSIX doesn't require getopt.h, and so rightfully it's missing on AIX.
However, gengetopt insists on getopt.h, so we just create a stub if
the system getopt.h is nowhere to be found.

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
chore, up xopen source minimum (as we need memmem())

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
chore, PEBKAC, list getopt.h.in as DIST

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
chore, guard-define SPLICE_F_MOVE if not supported

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
chore, include headers for splice()

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
chore, define _ALL_SOURCE for memmem()

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
chore, provide getopt_long() portability function in .ggo gen'd files

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
hygiene, mark unused parameters as such

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
chore, only link with -lutil if pty.h is present

Signed-off-by: Sebastian Freundt <freundt@ga-group.nl>
Merge branch 'bld/aix'

* bld/aix:
  chore, only link with -lutil if pty.h is present
  hygiene, mark unused parameters as such
  chore, provide getopt_long() portability function in .ggo gen'd files
  chore, define _ALL_SOURCE for memmem()
  chore, include headers for splice()
  chore, guard-define SPLICE_F_MOVE if not supported
  chore, PEBKAC, list getopt.h.in as DIST
  chore, up xopen source minimum (as we need memmem())
  minor, generate a stub getopt.h when none can be found during configure time
  chore, actually check for pty.h
  minor, conditionalise pseudo-tty support on HAVE_PTY_H