Store vector metatable in registry

builtin/common/tests/misc_helpers_spec.lua

@@ -1,4 +1,5 @@
 _G.core = {}
+_G.vector = {metatable = {}}
 dofile("builtin/common/vector.lua")
 dofile("builtin/common/misc_helpers.lua")
 

builtin/common/tests/serialize_spec.lua

@@ -1,4 +1,5 @@
 _G.core = {}
+_G.vector = {metatable = {}}
 
 _G.setfenv = require 'busted.compatibility'.setfenv
 

builtin/common/tests/vector_spec.lua

@@ -1,4 +1,4 @@
-_G.vector = {}
+_G.vector = {metatable = {}}
 dofile("builtin/common/vector.lua")
 
 describe("vector", function()

builtin/common/vector.lua

@@ -6,10 +6,8 @@ Note: The vector.*-functions must be able to accept old vectors that had no meta
 -- localize functions
 local setmetatable = setmetatable
 
-vector = {}
-
-local metatable = {}
-vector.metatable = metatable
+-- vector.metatable is set by C++.
+local metatable = vector.metatable
 
 local xyz = {"x", "y", "z"}