modules/renumber: rename a module-global variable

... to avoid shadowing which broke lint:other in CI.
And add NEWS entry.

NEWS

@@ -19,6 +19,7 @@ Improvements
 Bugfixes
 --------
 - correctly use EDNS(0) padding in failed answers (!921)
+- policy and daf modules: fix reroute rules (!901)
 
 
 Knot Resolver 4.3.0 (2019-12-04)

modules/renumber/renumber.lua

 -- Module interface
 local ffi = require('ffi')
-local prefixes = {}
+local prefixes_global = {}
 
 -- Create subnet prefix rule
 local function matchprefix(subnet, addr)
@@ -28,7 +28,7 @@ end
 
 -- Add subnet prefix rewrite rule
 local function add_prefix(subnet, addr)
-	table.insert(prefixes, matchprefix(subnet, addr))
+	table.insert(prefixes_global, matchprefix(subnet, addr))
 end
 
 -- Match IP against given subnet or record owner
@@ -119,7 +119,7 @@ end
 
 -- Layers
 M.layer = {
-	finish = rule(prefixes),
+	finish = rule(prefixes_global),
 }
 
 return M