Update signature warning

[Bidouille]

During registering process, we have a control on the signature field.
In english:

Invalid signature, valid examples include:
OpenOffice 3.1 on Windows Vista / NeoOffice 2.2.3 with MacOS 10.4 / OpenOffice 2.4 on Ubuntu 9.04

In french:

Signature invalide, quelques exemples corrects :
OpenOffice 2.4 sous Windows XP / NeoOffice 2.2.3 sous MacOS 10.4 / OpenOffice 2.3 sous Ubuntu Gutsy

These versions are all obsolete.
Maybe an update with newer will be fine.

[Hagar Delest]

On the other hand, this obsolete signature helps to spot the spammers.