Merge from 0.21.x branch: Prepare for 0.21.1 release.
* gettext-runtime/doc/matrix.texi: Update from TP.
* gettext-runtime/doc/nls.texi (STATUS): Update.
* gettext-runtime/intl/libgnuintl.in.h (LIBINTL_VERSION): Bump.
* gettext-tools/libgettextpo/gettext-po.in.h (LIBGETTEXTPO_VERSION): Bump.
* libtextstyle/version.sh: Update VERSION_NUMBER, RELEASE_DATE.
* NEWS, gettext-runtime/NEWS: Update.
* libtextstyle/lib/Makefile.am (LTV_*): Bump to 1:2:1.
* gettext-runtime/intl/Makefile.am (LTV_*): Bump to 11:0:3.
* gettext-tools/libgettextpo/Makefile.am (LTV_*): Bump to 5:8:5.
* gettext-runtime/src/envsubst.c: Update copyright years of the --version output.
* gettext-runtime/src/gettext.c: Likewise.
* gettext-runtime/src/gettext.sh.in: Likewise.
* gettext-runtime/src/ngettext.c: Likewise.
* gettext-tools/misc/autopoint.in: Likewise.
* gettext-tools/misc/convert-archive.in: Likewise.
* gettext-tools/misc/gettextize.in: Likewise.
* gettext-tools/src/cldr-plurals.c: Likewise.
* gettext-tools/src/hostname.c: Likewise.
* gettext-tools/src/msgattrib.c: Likewise.
* gettext-tools/src/msgcat.c: Likewise.
* gettext-tools/src/msgcmp.c: Likewise.
* gettext-tools/src/msgcomm.c: Likewise.
* gettext-tools/src/msgconv.c: Likewise.
* gettext-tools/src/msgen.c: Likewise.
* gettext-tools/src/msgexec.c: Likewise.
* gettext-tools/src/msgfilter.c: Likewise.
* gettext-tools/src/msgfmt.c: Likewise.
* gettext-tools/src/msggrep.c: Likewise.
* gettext-tools/src/msginit.c: Likewise.
* gettext-tools/src/msgmerge.c: Likewise.
* gettext-tools/src/msgunfmt.c: Likewise.
* gettext-tools/src/msguniq.c: Likewise.
* gettext-tools/src/recode-sr-latin.c: Likewise.
* gettext-tools/src/urlget.c: Likewise.
* gettext-tools/src/xgettext.c: Likewise.
* gettext-tools/configure.ac (ARCHIVE_VERSION): Bump to 0.21.1.
* gettext-tools/misc/autopoint.in: Allow version 0.21.1.
