That was an intentional change by Mozilla. You can use the Menu Editor add-on to rearrange menu items - https://addons.mozilla.org/firefox/addon/menu-editor

Dear friend, the problem is that there is exchange of something very useful from users an this break them habits! I'm not interested of forced using of tools! Of course it's good that there is a tool to solve my problem, but this action make me unhappy. last words - this is the way of losing users.

check the answer by cor-el on below link. works fine no editor addon needed

http://support.mozilla.com/en-US/questions/791244