bug#9130: Document Lisp mode fontification for strings after :documentation

[Eli Zaretskii]

> Date: Wed, 30 Dec 2015 11:52:38 +0530
> From: Shakthi Kannan <shakthimaan@gmail.com>
> Cc: bug-gnu-emacs@gnu.org
> 
> I have received the docstrings for the three functions from the
> author, Robert Brown, and I am re-submitting the patch.

Thanks, pushed with some changes.  Please see how I changed the doc
strings for conformance with Emacs coding style: the first line of the
doc string must be a full sentence.  If the first sentence is too long
for that, make it shorter, omitting some details for the rest of the
doc string.