support Python Mutator for winafl

[peternguyen93]

allow user can write their custom mutator in Python

[googlebot]

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[ifratric]

Hey,
First of all thank you for sending the PR and sorry about the late reply - I'm on vacation currently.

Please note that I can only accept PRs from contributors that signed the Google CLA. If you want to proceed, please sign it and reply here so that the bot can recheck it.

Secondly, GitHub currently reports all lines in the files as being changed (see the "files changed" tab in this PR) - possibly you changed the line breaks? I realize that formatting in WinAFL sucks (mostly my fault due to using VS IDE for the project and being too lazy to change any of the defaults), but unfortunately, changing it makes it impossible to review the PR as I have no idea which lines to review.