lbaselib cleanup

[bobtfish]

No description provided.

[khvzak]

FYI, t is used in the original code, but the large part to do API checks is missing (probably due to transpiling flags)
Eg:

  luaL_argcheck(L, t == LUA_TNIL || t == LUA_TTABLE, 2,
                    "nil or table expected");

See https://github.com/lua/lua/blob/v5.3/lbaselib.c#L128