Fix for Firefox 45+ issues with dark themes under XFCE 4 / GTK3

After upgrading to Linux Mint 14.04.3, using a dark theme, as its better on my rather crappy eyes, I ran into that nasty issue with input fields again (black text on dark background or white text on nearly white background). Thought that was a thing of the past, but .... no.

Fix for location bar issue (old bar extension) in Firefox 43+

While setting up my new system (Linux Mint 17.3 XFCE / Mintbuntu), I discovered this nasty bug with the Old Location Bar extension, which had "moz-action:" and some JS garbage always appearing in the search dropdown, whenever I was typing something into the location / address bar.