Add a library object builder

Author: TomDotBat

sh_messagepack.lua

@@ -5,6 +5,7 @@
 --]]
 
 messagePack = {}
+messagePack.__index = messagePack
 
 local SIZEOF_NUMBER = 8
 local maxinteger
@@ -841,4 +842,8 @@ else
     end
 end
 
-set_array("without_hole")
+set_array("without_hole")
+
+function messagePack.new()
+    return setmetatable({}, messagePack)
+end