[oe] [PATCH] usermanual : update note about PR

[Rolf Leggewie]

Frans Meulenbroeks wrote:
> Apart from the good practice, it also might help a little bit to give
> PR a standard location.

PR does have a standard location as defined in the StyleGuide, although
of course it may not be observed in all recipes.

http://wiki.openembedded.org/index.php/Styleguide