Add copyright notices in several files.

Add copyright notices in several files.

Reported by <ineiev@gnu.org> in <https://savannah.gnu.org/bugs/?54809>.

* gettext-runtime/m4/Makefile.am: Add GPL copyright notice.
* gettext-tools/m4/Makefile.am: Likewise.
* gettext-tools/doc/iso-639.sed: Likewise.
* gettext-tools/doc/iso-639-2.sed: Likewise.
* gettext-tools/doc/iso-3166.sed: Likewise.
* gettext-tools/its/glade1.its: Likewise.
* gettext-tools/its/glade2.its: Likewise.
* gettext-tools/its/gsettings.its: Likewise.
* gettext-tools/its/gtkbuilder.its: Likewise.
* gettext-tools/misc/cvsuser.c: Likewise.
* gettext-tools/projects/team-address: Likewise.
* gettext-tools/projects/GNOME/team-address: Likewise.
* gettext-tools/projects/GNOME/trigger: Likewise.
* gettext-tools/projects/KDE/team-address: Likewise.
* gettext-tools/projects/KDE/trigger: Likewise.
* gettext-tools/projects/TP/team-address: Likewise.
* windows/windres-options: Likewise.
* gettext-runtime/po/insert-header.sin: Add copyright notice, based on the one
in Rules-quot.
* gettext-tools/doc/FAQ.html: Add copyright notice, suitable for documentation.