Make sure numbers are numbers

[Henk Boom <henk@...>]

I just fixed a subtle bug in my serialization/deserialization
functions for a data structure, where objects that were serialized
then deserialized looked identical but behaved slightly differently.
It was caused by something like this:

> return 9 < 10
true
> return "9" < "10"
false

Lesson learned: make sure to use tonumber() on numbers you extract
from strings...

It also boost the importance of frequent type checking in my mind, and
makes me hate automatic string->number coercion a little bit more :p

    henk