bit32 for gopher-lua

Implements Lua 5.2 bit32 for gopher-lua. To use, call

import (
	"github.com/PeerDB-io/gluabit32"
)

// add so that `local bit32 = require("bit32")` works
L.PreloadModule("bit32", gluabit32.Loader)

// or add to global env
L.Push(ls.NewFunction(gluabit32.Loader))
L.Call(0, 1)
L.Env.RawSetString("bit32", L.Get(-1))
L.Pop(1)