python: 2.7.9rc1 devel

ensurepip is backported to 2.7.9; use that to get pip instead of staging pip and setuptools ourselves.
After understanding what it takes to make this work cleanly I don't see a compelling reason to use ensurepip; PEP 453 makes it clear that they don't care what repackagers do to install pip as long as pip ends up installed. It's more robust to install setuptools and pip ourselves. I'll roll this back.