ssl_support: Adjust to tunneling changes in Python 2.7.7 and 3.4.1.

Since Python 3 will always need the _execfile functionality (to fulfill the test in test_sandbox), this functionality should become part of the core implementation.

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extra : histedit_source : fba32276bb6acd7b5e44ff596407d10c94c618a9

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extra : histedit_source : 7600ecd3914abc4767d4296f62b038a6397df673

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extra : amend_source : 371b48777dba5d8a4d62b5899944471752f830bd
extra : histedit_source : 0739a1da7f11a5f6e348a34b203a9328d0bc0f22

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extra : amend_source : 272b2718bac5934550a589d08f584120ba78086a

Make memoized zip manifests opt-in using the PKG_RESOURCES_CACHE_ZIP_MANIFESTS environment variable. Ref #154.

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extra : amend_source : 7754d23956c4157235dca41e90f05c29691078ee

The fix for https://bugs.python.org/issue7776 changed httplib.HTTPConnection's
handling of tunneling: `host' now points to the proxy host, so we have to
adjust the code to perform the certificate validation on `_tunnel_host' instead
when it is available.

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extra : amend_source : 9576c3d20e8d3bcb3b951cd2f588e782f885ebe6

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extra : amend_source : a25cd725094883d738e9c37cd71e3ac3a946d9fe

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extra : amend_source : fa41c3fb787b667f703f67a52aed7a2958e615b4

Extract method for generating lines for a pkg in nsp. Fixes issue in 67bdf3a726962 where only the last dat would be written.