Add encoding directives for unibyte GNU Emacs.

(Thanks to Garrett Wollman for reporting the problem.)
* NEWS, Theory, northamerica: Add "coding: utf-8" directives so
that GNU Emacs, when run in a unibyte locale, does not mistakenly
interpret these files to be unibyte.  This change should make no
difference if you use Emacs to read these files in a UTF-8 locale.
I didn't bother to add coding directives to files where GNU Emacs
already deduces the encoding correctly in a Latin-1 locale.