Update after gnulib changed.
* gettext-runtime/intl/arg-nonnull.h: Update from gnulib.
* gettext-runtime/intl/localename.c: Likewise.
* gettext-runtime/intl/lock.h: Likewise.
* gettext-runtime/intl/relocatable.c: Likewise.
* gettext-runtime/intl/relocatable.h: Likewise.
* gettext-runtime/intl/threadlib.c: Likewise.
* gettext-runtime/intl/vasnprintf.c: Likewise.
* gettext-runtime/intl/verify.h: Likewise.
* gettext-runtime/intl/xsize.h: Likewise.
* gettext-runtime/libasprintf/vasnprintf.c: Likewise.
* gettext-runtime/m4/fcntl-o.m4: Likewise.
* gettext-runtime/m4/iconv.m4: Likewise.
* gettext-runtime/m4/flexmember.m4: Update copyright years.
* gettext-runtime/m4/intlmacosx.m4: Likewise.
* gettext-runtime/m4/inttypes_h.m4: Likewise.
* gettext-runtime/m4/nls.m4: Likewise.
* gettext-runtime/m4/po.m4: Likewise.
* gettext-runtime/m4/progtest.m4: Likewise.
* gettext-runtime/m4/size_max.m4: Likewise.
* gettext-runtime/m4/stdint_h.m4: Likewise.
* gettext-runtime/m4/xsize.m4: Likewise.
* Makefile.am (distcheck-hook): Update.
