Start 3.6.0rc1. (Note, patch level was incorrectly set to 3.6.0b4+ following b3. It is now b4+ again.)

Issue #27100:  With statement reports missing __enter__ before __exit__.  (Contributed by Jonathan Ellington.)

Issue #26163:  Disable periodically failing test which was overly demanding of the frozenset hash function effectiveness

Issue 28587:  list.index documentation missing start and stop arguments. (Contributed by Mariatta Wijaya.)

Allow AF_UNIX in create_server & create_connection

Issue 28475:  Improve error message for random.sample() with k < 0. (Contributed by Francisco Couzo).

close issue28172: Change all example enum member names to uppercase, per Guido; patch by Chris Angelico.

The Python 3.5 change must not be applied to Python 3.6.

Reloading the warnings module duplicates filters in warnings.filters. Fixing
the issue is tricky. It was decided to simply remove the check from Python 3.5,
since the bug only impacts Python unit tests, not real applications.

The check is kept in Python 3.6 and newer.

Issue #28727: Regular expression patterns, _sre.SRE_Pattern objects created by
re.compile(), become comparable (only x==y and x!=y operators). This change
should fix the issue #18383: don't duplicate warning filters when the warnings
module is reloaded (thing usually only done in unit tests).

Patch by Xiang Zhang.

The fields ml_name and ml_doc are of type "const char *" rather of "char *".

The fields ml_name and ml_doc are of type "const char *" rather of "char *".