[ELPA] :doc with "README.org" doesn't rename exported texi file correctly

[Adam Porter]

Hi Stefan, Philip, et al,

I noticed that, even though the `ement' recipe in `elpa-packages' has 
the same :doc setting as some other packages:

  ("ement" :url "https://github.com/alphapapa/ement.el.git";
    :doc "README.org"
    :auto-sync t)

...the Info manual generated from its readme is not available for 
viewing in Emacs after the package is installed.  To solve that, I had 
to add this line to the readme (learning from other packages in ELPA):

  #+EXPORT_FILE_NAME: ement.texi

It would seem like this file naming ought to be handled automatically by 
the build scripts.  Or, at least, it should be documented that this is 
required, otherwise package authors are left to trial-and-error and 
releasing new versions until it works.  :)

What do you think?

Thanks,
Adam