bump(dev-lang/python): Sync with upstream python-2.7.5-r4

Copy of upstream 2.7.5-r4 + cross compile tweaks/fixes from our -r2
Dropped some sed hackery related to ChromiumOS's /usr/local weirdness.
I am hoping that issue18851.patch fixes some intermittent build issues.
Merge pull request #297 from marineam/python

bump(dev-lang/python): Sync with upstream python-2.7.5-r4