posix_spawn_file_actions_addclose: Work around Solaris 11 2011-11 bug.

posix_spawn_file_actions_addclose: Work around Solaris 11 2011-11 bug.

* m4/spawn_h.m4 (gl_SPAWN_H_DEFAULTS): Initialize
REPLACE_POSIX_SPAWN_FILE_ACTIONS_ADDCLOSE.
* m4/posix_spawn.m4 (gl_POSIX_SPAWN_BODY): Define
HAVE_WORKING_POSIX_SPAWN.
(gl_FUNC_POSIX_SPAWN_FILE_ACTIONS_ADDCLOSE): New macro.
* lib/spawn.in.h (posix_spawn_file_actions_addclose): Test
REPLACE_POSIX_SPAWN_FILE_ACTIONS_ADDCLOSE, not REPLACE_POSIX_SPAWN.
* lib/spawn_faction_addclose.c: Add workaround implementation if
HAVE_WORKING_POSIX_SPAWN.
* modules/spawn (Makefile): Substitute
REPLACE_POSIX_SPAWN_FILE_ACTIONS_ADDCLOSE.
* modules/posix_spawn_file_actions_addclose (configure.ac): Invoke
gl_FUNC_POSIX_SPAWN_FILE_ACTIONS_ADDCLOSE. Test
REPLACE_POSIX_SPAWN_FILE_ACTIONS_ADDCLOSE, not REPLACE_POSIX_SPAWN.
(Depends-on): Update conditions.
* doc/posix-functions/posix_spawn_file_actions_addclose.texi: Mention
the Solaris 11 bug.