Lowercase text after full stop on describe-variable

[Juanma Barranquero]

When a variable is obsolete, the help info looks ugly because the "not
documented as a variable" text is not capitalized after a full stop.

Example from local-write-file-hooks:

> Documentation:
> This variable is obsolete since 21.4.
> Use `write-file-functions' instead.
> not documented as a variable.

Perhaps it is better to put the obsolescence info after the variable
documentation, unless the current point was purposelly chosen to
highlight the fact that the variable is obsolete.


                                                           /L/e/k/t/u