Fix claims about emacs support in the reference manual

We stopped shipping this some time ago, as it was (a) outdated
and (b) the FSF asked us to. So don't claim we ship them, instead
point to a better alternative.

doc/ref/mloop.xml

@@ -1296,8 +1296,7 @@ and read in the edited file automatically.
 <Index Key="vim"><C>vim</C></Index>
 <Index Key="emacs"><C>emacs</C></Index>
 In the <F>etc</F> subdirectory of the &GAP; installation
-we provide some setup files for the editors <C>vim</C> and
-<C>emacs</C>/<C>xemacs</C>.
+we provide some setup files for the editor <C>vim</C>.
 <P/>
 <C>vim</C> is a powerful editor that understands the basic <C>vi</C> commands
 but provides much more functionality. You can find more information about it
@@ -1335,8 +1334,10 @@ augroup END
 See the headers of the two mentioned files for additional comments and
 adjust details according to your personal taste.
 Send comments and suggestions to <Email>support@gap-system.org</Email>.
-Setup files for <C>emacs</C>/<C>xemacs</C> are contained in the
-<F>etc/emacs</F> subdirectory.
+<P/>
+Users of <C>emacs</C>/<C>xemacs</C> may wish to take a look at the
+<URL Text="major-mode for editing GAP files">https://melpa.org/#/gap-mode</URL>
+by Ivan Andrus.
 
 </Section>