Add completions for sox

[xyproto]

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sox is a collection of executables and libraries that has been in Debian since 1997. It has also been in Arch Linux for at least 10 years (probably longer). It is available for most (all?) Linux distros.

I would argue that sox is more well known, and has more installations, than "the Play Framework for Java and Scala".

This PR proposes to replace _play (for "The Play Framework") with one for the play executable that comes with sox, and also add completions for sox, soxi and rec.