It’s been a while since I added anything to this project, but today I uploaded Proper Buttons for Firefox 29 and above. This replaces the Firefox Back and Forward buttons with regular back and forward buttons, and it replaces the Urlbar Stop and Reload buttons with regular stop and reload buttons. Left click, middle click and right click functionality is preserved. After installing the extension don’t forget to put the buttons on your toolbar.
Note that the stop and reload buttons are not combined. If the buttons were combined then the Duplicate Tab function of the Reload button (middle-click) would be inaccessible while a page was loading in that tab. You could still duplicate a tab by ctrl-dragging, but I think this is less well known and less convenient. In a future version I may add a Duplicate Tab item to the Tab Context Menu, and maybe an option to combine Stop and Reload.