[docs] [issue19391] Fix PCbuild/readme.txt in 2.7 and 3.3

[Zachary Ware]

Zachary Ware added the comment:

Thanks for the lesson, Vajrasky and David, and thank you for the review Brian.

The final commit did have a couple changes not in the posted patch, just fixes of the same two obvious typos in both branches (avalible -> available, lniked -> linked).

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resolution:  -> fixed
stage: patch review -> committed/rejected
status: open -> closed

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue19391>
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