Some localized text strings missed on po files

[Fantu]

Hi I did a fast update of italian language (Fantu@99f94d0 free to take the patch and apply it if you think it useful) and testing it (rebuilding 2.5 package) I found that there are some text strings missed in the po file, for example "User Name" and "Log in" of login page, "Activity Log" of menu, "Plugin description" ecc...