Hello,

I apologize for my "oops I figured it out immediately after I sent the
email" syndrome.  I was trying to find the answer in the bug reports
when the answer was in the code and quite obvious.

Anyways here is a patch that unconditionally enables imenu but checks
the return value of mutool and will raise an imenu-unavailable-error
when it is not successful.  However, that error stops docview from
displaying the document so I decided to put the setup function in a hook
so the error occurs after the document is displayed.

I looked briefly for documentation on how errors work in hooks but could
not find any.  I don't want this error to prevent the other hooks from
being run (which would be user defined hooks.  we don't currently use
this hook).

Thanks,

Morgan