Patch by Donald Stufft and Nick Coghlan

delaying the main thread so that it doesn't race ahead of the workers.

(issue #16685).

Merge with 3.3 for Issue #19544 and Issue #6286. Merge is untested. I was unable to test due to bab0cbf86835.

Issue #19544 and Issue #6286: Restore use of urllib over http allowing use of http_proxy for Distutils upload command, a feature accidentally lost in the rollback of distutils2.

Issue 19544 and Issue #7457: Restore the read_pkg_file method to distutils.dist.DistributionMetadata accidentally removed in the undo of distutils2.

Removed support for strings.

of size 8: wcscmp (wcscmp.S:464))

of size 8: wcscmp (wcscmp.S:464))

stable ABI