thirdparty: split glue code into expansions

init/modules.xml

@@ -33,6 +33,8 @@
   <Include file="..\modules\cooldown.lua"/>
   <Include file="..\modules\tooltip.lua"/>
   <Include file="..\modules\thirdparty.lua"/>
+  <Include file="..\modules\thirdparty-vanilla.lua"/>
+  <Include file="..\modules\thirdparty-tbc.lua"/>
   <Include file="..\modules\buff.lua"/>
   <Include file="..\modules\buffwatch.lua"/>
   <Include file="..\modules\nameplates.lua"/>

modules/thirdparty-tbc.lua

@@ -0,0 +1,5 @@
+pfUI:RegisterModule("thirdparty-tbc", "tbc", function ()
+  -- abort when thirdparty core module is not loaded
+  if not pfUI.thirdparty then return end
+  local rawborder, default_border = GetBorderSize()
+end)