enhancement in jMailer file driver

[bastnic]

Laurent recently add a file driver for jMailer which I think it's a very great idea during dev.

But if more than one mail is sent in the same second, only one file is generated. So I add a little random pattern. I used jAuth::getRandomPassword which I don't think it's a good idea for jelix core.

Furthermore, I add a little return to line between header and body

[laurentj]

This dependency with jAuth is not good.

[Julien]

you may use

$token = uniqid(mt_rand(), true);

there are still collision risks if mt_rand() returns the same value and both intructions are called in the same microsecond, but that's quite improbable.

[laurentj]

Fixed the issue in changeset http://hg.jelix.org/jelix/jelix-trunk/rev/319c81b9a1ec

thanks Bastnic and Julien.