Make Firefox hide menubar by default

[lewtds]

The default for Firefox on Windows and most Linux distros is to hide the menubar and show the Firefox button on the top left instead. But with Ubuntu, since they have the globalmenu, they want Firefox to show that menu by default. We prefer the first approach.

[myguidingstar-zz]

really? I prefer traditional menu. I find it more accessible

[lewtds]

Many people (including me) appreciated a few more saved vertical pixels.