The overloading of IR emits magic \X'...' sequences that turn into HTML manual links.
But not all such IR invocations should be manual links;
those had to be written to avoid the IR macro before.
Worse, the \X'...' ending the IR causes troff to emit only a single space after a period.
Defining a new IM macro for manual references fixes both problems.
Fixes#441.
Add -x flag to mklatinkbd to generate file for $HOME/.XCompose.
Thanks to Anthony Martin, Tony Lainson, and Kris Maglione for legwork.
R=rsc
http://codereview.appspot.com/3811043