Fix auto-selection of URL field with X11 selection

Created by: dmedvinsky

We use focusin event instead of click because when using the latter, when the selection is created it isn't put into X11 PRIMARY selection. And as a Linux user I'm very used to such behaviour that when something gets selected, it's ready for pasting, which is the primary purpose of the clone URL field.

When focusin is used, the selection is copied to X11 buffer automatically, so it works as expected (tested in Firefox and Chrome).