build: Recover and update *.m4.
* m4/lib-ld.m4, m4/lib-link.m4, m4/lib-prefix.m4: Copied from gnulib. * m4/po.m4, m4/nls.m4, m4/progtest.m4: Likewise. * m4/gettext.m4, m4/iconv.m4: Update from gnulib. * m4/host-cpu-c-abi.m4: New from gnulib.
- Fixes-commit: 980e4410bb0a372a7bcce5f454915e6565a56b96
- Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>