Pay attention about redefinition of undefined.

[meh]

undefined can be set to something else, as in, undefined is a valid variable name, we should find a way to avoid redefinition of undefined.

The best way to go with this is to add var undefined at the beginning of each function, or find a better way to avoid cluttering up everything.

[adambeynon]

Well we can be quite liberal with var undefined as minifying the result will remove any that aren't used, so this seems a good idea- we can't trust what users do in their code.