Further refactoring

This should finish the work to make all globals to local variables.
That allows LuaJIT to properly compile things by interning the
references to the relevant parts (rather than looking up globals
all the time which stops a trace).

frontend/document/koptinterface.lua

@@ -2,6 +2,9 @@ local Document = require("document/document")
 local Cache = require("cache")
 local CacheItem = require("cacheitem")
 local Screen = require("ui/screen")
+local Geom = require("ui/geometry")
+local TileCacheItem = require("document/tilecacheitem")
+local Dbg = require("dbg")
 -- TBD: KOPTContext
 
 local KoptInterface = {