generating code for inaccessible constructor is unnecessary

[c3076802]

Say we have a class call AppConfigMgr has a private constructor only, ulua will export some unnecessary code

    public class AppConfigMgr  {
        private AppConfigMgr()
        {

        }

new LuaMethod("New", _CreateConfigs_AppConfigMgr),

static int _CreateConfigs_AppConfigMgr(IntPtr L)
    {
        LuaDLL.luaL_error(L, "Configs.AppConfigMgr class does not have a constructor function");
        return 0;
    }

Don't generate New when the constructor is inaccessible, Let lua handle the error when miss use.

Thank you