posix_spawn_file_actions_adddup2: Work around Solaris 11 2011-11 bug. * m4/spawn_h.m4 (gl_SPAWN_H_DEFAULTS): Initialize REPLACE_POSIX_SPAWN_FILE_ACTIONS_ADDDUP2. * m4/posix_spawn.m4 (gl_FUNC_POSIX_SPAWN_FILE_ACTIONS_ADDDUP2): New macro. * lib/spawn.in.h (posix_spawn_file_actions_adddup2): Test REPLACE_POSIX_SPAWN_FILE_ACTIONS_ADDDUP2, not REPLACE_POSIX_SPAWN. * lib/spawn_faction_adddup2.c: Add workaround implementation if HAVE_WORKING_POSIX_SPAWN. * modules/spawn (Makefile): Substitute REPLACE_POSIX_SPAWN_FILE_ACTIONS_ADDDUP2. * modules/posix_spawn_file_actions_adddup2 (configure.ac): Invoke gl_FUNC_POSIX_SPAWN_FILE_ACTIONS_ADDDUP2. Test REPLACE_POSIX_SPAWN_FILE_ACTIONS_ADDDUP2, not REPLACE_POSIX_SPAWN. (Depends-on): Update conditions. * doc/posix-functions/posix_spawn_file_actions_adddup2.texi: Mention the Solaris 11 bug.