Issue #17744: Now unset VIRTUAL_ENV environment variable when deactivating.
Closes #17744: Merged fix from 3.3.
Issue #17743: Now use extended syntax of set command in .bat files.
Closes #17743: Merged fix from 3.3.
#14146: Highlight source line while debugging on Windows.
#14146: merge with 3.3.
Issue #17683: socket module: return AF_UNIX addresses in Linux abstract
namespace as string.
Backed out changeset c0f2b038fc12
Issue #17900: Allowed pickling of recursive OrderedDicts.  Decreased pickled
size and pickling time.
#17973: fix technical inaccuracy in faq entry (it now passes doctest).
merge #17973: fix technical inaccuracy in faq entry (it now passes doctest).
Fix issue #17996: expose socket.AF_LINK constant on BSD and OSX.