Update lua client to 0.0.1-24

The new version of the lua client uses libmpack as a backend, and some test
scripts had to be updated to reflect that.

test/functional/ui/screen.lua

@@ -138,7 +138,7 @@ do
     -- this is just a helper to get any canonical name of a color
     colornames[rgb] = name
   end
-  session:exit(0)
+  session:close()
   Screen.colors = colors
   Screen.colornames = colornames
 end