Adding the US Extended Keyboard layout for changes.

Change input source wouldn't work with the US Extended Keyboard layout without
this patch. All that was missing was the definition of a constant.
Getting vim ubiquitous mode to work inside Firefox.

I couldn't see any reason the vim ubiquitous mode was disabled in Firefox. I
see a lot of benefit in using the convenient vim key bindings inside Firefox.
Preventing the makefile from changing PATH

This was screwing up the indirection rbenv provided while adding nothing to the
build.