Prepare for 0.21 release.

Prepare for 0.21 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.
* gettext-runtime/po/Makefile.in.in: Bump Origin version.
* NEWS, libtextstyle/NEWS, gettext-runtime/NEWS: Update.
* libtextstyle/lib/Makefile.am (LTV_*): Bump to 1:1:1.
* gettext-runtime/intl/Makefile.am (LTV_*): Bump to 10:0:2.
* gettext-tools/libgettextpo/Makefile.am (LTV_*): Bump to 5:7:5.
* gettext-tools/configure.ac (ARCHIVE_VERSION): Bump to 0.21.
* gettext-tools/misc/autopoint.in: Allow version 0.21.