libjpeg-turbo: update 1.3.0 -> 1.3.1

This commit also modifies SRC_URI to fetch a release tarfile instead
of checking out from SourceForge SVN and makes some minor updates to
the jpeg-tools DESCRIPTION text.

Signed-off-by: Andre McCurdy <armccurdy@gmail.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>