Reject extra arguments to .new(), etc.

[jwdevel]

If I have a type bound to Lua, I can construct like so:

v = vec4.new(1,2,3,4)

However, .new will also take any extra arguments and ignore them:

v = vec4.new(1,2,3,4,'foo', 'bar?')
-- v is a valid vec4, no error

Maybe these cases should be rejected?

This can lead to confusion if we hav, eg. vec2, vec3, vec4, like so:

-- It looks like we meant to create vec4
-- If we don't notice the '2' character, it is confusing.
v = vec2.new(10,20,30,40)

I don't know kaguya's internals, but couldn't the constructor (or other functions) check lua_gettop when they're called?