Fix melpa installation

[Katsumi Yamaoka <yamaoka@xxxxxxx>]

In [emacs-w3m:13554]
On Fri, 13 Sep 2019 17:14:11 +0900, Katsumi Yamaoka wrote:
> I posted an isseue message as:
> <https://github.com/melpa/melpa/issues/6435>

I made a change so to make emacs-w3m create the w3m-load.el file
if it is missing in the melpa installation after all, and changed
the recommended recipe for getting started emacs-w3m as follows:

,---- <https://emacs-w3m.github.io/index.html#configuration>
| Emacs-w3m has many configuration options, but the minimum that
| is required is just to put this line into your ~/.emacs file:
|
|     (require 'w3m-load)
|
|     If you have installed emacs-w3m from MELPA, there is no
|     w3m-load.el file initially, so we recommend using instead
|     this in order to create the w3m-load.el file:
|
|         (condition-case nil
|             (require 'w3m-load)
|           (file-error (require 'w3m)))
|
|     Once the w3m-load.el file is created by w3m.elc, you may
|     replace the above form with the one-line setting (if you
|     want), i.e.:
|
|         (require 'w3m-load)
|
|     If the w3m-load.el file is not created, make sure if the
|     file ~/.emacs.d/elpa/archives/melpa/archive-contents
|     exists.
|
| And then, just type M-x w3m, and you can use emacs-w3m.
`----

The condition-case form there will load w3m.elc and it creates
the w3m-load.el file if it is missing.  It also tries to pick up
from the "~/.emacs.d/elpa/archives/melpa/archive-contents" file
the original revision hash value for the `emacs-w3m-git-revision'
constant, and the melpa timestamp used in the directory name like
"~/.emacs.d/elpa/w3m-20190918.9999/".  If the timestamp and the
directory name are mismatched, it will prompt a user to update
the installation.  Please let me know if this causes any trouble.

Thanks.
Regards,