SquirrelMail 1.5.1 locales

This is first SquirrelMail 1.5.1 locales release for SquirrelMail 1.5.1
version.

2006-02-19 (1.5.1 release)
 - Branched from HEAD.
 - Removed 1.4.6cvs strings from squirrelmail.pot.