gnome-doc-utils string change

[Shaun McCance <shaunm gmail com>]

Regrettably, I had to change the string ", " in gnome-doc-utils to
the more obscure "<msgstr>, </msgstr>".  That extra msgstr wrapper
is ignored by my i18n stylesheets.  Its only purpose is to prevent
intltool from mangling the very important trailing whitespace.

On the plus side, I put in a much better comment explaining the
purpose of this string.

--
Shaun