python313: mpdecimal: please test wip/mpdecimal

[Thomas Klausner <wiz%NetBSD.org@localhost>]

Hi!

When compiling python313 one sees:

configure: WARNING: no system libmpdecimal found; falling back to bundled libmpdecimal (deprecated and scheduled for removal in Python 3.15)

So I'd like to switch python313 to using libmpdecimal after the
branch.

As a first step, I've updated wip/mpdecimal to the current
version. All its self tests pass for me on NetBSD-10.99.12/amd64.

Please try the package and the self tests ('make test') on other
operating systems or versions, especially if you're using python313.

Thank you,
 Thomas