Mail footer files not correct

[ThomasDieckmann]

Steps to reproduce

1. just look at core/templates/html.mail.footer.php and core/templates/plain.mail.footer.php
2. after the two "--" characters, there's a space missing to separate the signature as described at https://en.wikipedia.org/wiki/Signature_block

Expected behaviour

Mail programs should be able to recognize and separate the signature

Actual behaviour

The signature isn't recognized

Unfortunately I can't attach the corrected PHP files. So, I had to rename them.

plain.mail.footer.php.txt html.mail.footer.php.txt