NS port horizontal scroll-bars

[Alan Third]

I've been trying to complete the horizontal scroll-bars implementation
in the NS port and have run into a bit of a problem I can't work out.

They display correctly, and when you click on them they, I think, send
a correctly formatted emacs_event, but nothing happens. Vertical
scroll-bars work as expected.

Have I missed somewhere where I need to enable the horizontal
scroll-bar events or something? Any pointers would be appreciated.

I've attached a patch containing what I've done so far.
-- 
Alan Third

horiz-scrollers-argh.patch
Description: Horizontal scroll-bars patch