version: use a tuple internally.
version: use a tuple internally.

As Avi suggested, we can use a tuple to make some comparisons more natural.
However, instead of doing a make_tuple on the comparison only, we can go
further and store the tuple internally.

I am still keeping the outer type, so it can host convenience functions like
to_sstring() and current().

Signed-off-by: Glauber Costa <f8b79557d19b40666ebe336545a0b6178af65685@cloudius-systems.com>

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