maint: remove useless REPLACE_*_H macros There are still a few modules, like iconv_h.m4, that still use older paradigms where GNULIB_POSIXCHECK is unsupported and where gl_REPLACE_<HEADER>_H is still essential. But since we are moving away from that style, I see no reason to keep the idiom for the modules that don't need it. * m4/arpa_inet_h.m4 (gl_REPLACE_ARPA_INET_H): Delete. * m4/dirent_h.m4 (gl_REPLACE_DIRENT_H): Likewise. * m4/locale_h.m4 (gl_REPLACE_LOCALE_H): Likewise. * m4/poll_h.m4 (gl_REPLACE_POLL_H): Likewise. * m4/spawn_h.m4 (gl_REPLACE_SPAWN_H): Likewise. * m4/sys_ioctl_h.m4 (gl_REPLACE_SYS_IOCTL_H): Likewise. * m4/wchar_h.m4 (gl_REPLACE_WCHAR_H): Likewise. * m4/btowc.m4: Update callers. * m4/dirfd.m4: Likewise. * m4/duplocale.m4: Likewise. * m4/fchdir.m4: Likewise. * m4/fdopendir.m4: Likewise. * m4/inet_ntop.m4: Likewise. * m4/inet_pton.m4: Likewise. * m4/ioctl.m4: Likewise. * m4/mbrlen.m4: Likewise. * m4/mbrtowc.m4: Likewise. * m4/mbsinit.m4: Likewise. * m4/mbsnrtowcs.m4: Likewise. * m4/mbsrtowcs.m4: Likewise. * m4/poll.m4: Likewise. * m4/setlocale.m4: Likewise. * m4/wcrtomb.m4: Likewise. * m4/wcsnrtombs.m4: Likewise. * m4/wcsrtombs.m4: Likewise. * m4/wctob.m4: Likewise. * m4/wcwidth.m4: Likewise. * modules/posix_spawn: Likewise. * modules/posix_spawn_file_actions_addclose: Likewise. * modules/posix_spawn_file_actions_adddup2: Likewise. * modules/posix_spawn_file_actions_addopen: Likewise. * modules/posix_spawn_file_actions_destroy: Likewise. * modules/posix_spawn_file_actions_init: Likewise. * modules/posix_spawnattr_destroy: Likewise. * modules/posix_spawnattr_getflags: Likewise. * modules/posix_spawnattr_getpgroup: Likewise. * modules/posix_spawnattr_getschedparam: Likewise. * modules/posix_spawnattr_getschedpolicy: Likewise. * modules/posix_spawnattr_getsigdefault: Likewise. * modules/posix_spawnattr_getsigmask: Likewise. * modules/posix_spawnattr_init: Likewise. * modules/posix_spawnattr_setflags: Likewise. * modules/posix_spawnattr_setpgroup: Likewise. * modules/posix_spawnattr_setschedparam: Likewise. * modules/posix_spawnattr_setschedpolicy: Likewise. * modules/posix_spawnattr_setsigdefault: Likewise. * modules/posix_spawnattr_setsigmask: Likewise. * modules/posix_spawnp: Likewise. Signed-off-by: Eric Blake <eblake@redhat.com>