Pattern `[a-z]` with `IGNORECASE` flag can match to some non-ASCII characters.

Straightforward solution for this is using `IGNORECASE | ASCII` flag.
But users may subclass `Template` and override only `idpattern`. So we want to
avoid changing `Template.flags`.

So this commit uses local flag `-i` for `idpattern` and change `[a-z]` to `[a-zA-Z]`.

Reported by John Gamboa on docs@p.o at
https://mail.python.org/pipermail/docs/2017-June/031942.html

time.clock() and time.perf_counter() now use again C double
internally.

Remove also _PyTime_GetWinPerfCounterWithInfo(): use
_PyTime_GetPerfCounterDoubleWithInfo() instead on Windows.

* Move _PyTime_overflow() at the top
* Move assertion on numerator into _PyTime_ObjectToDenominator()
* PEP 7: add { ... } to if blocks

* Separated functions and constants descriptions in sections.
* Added a note about the limitations of timezone constants.
* Removed redundant lists from the module docstring.

Change the code example from using `get_history_length` to `get_current_history_length`.

bpo-31728: Prevent crashes in _elementtree due to unsafe cleanup of Element.text and Element.tail (#3924)

* Add _PyTime_GetPerfCounter()
* Use _PyTime_GetPerfCounter() for -X importtime

bpo-31701: On Windows, faulthandler.enable() now ignores MSC and COM
exceptions.

bpo-28280: Make PyMapping_Keys(), PyMapping_Values() and PyMapping_Items() always return a list (#3840)

With the upgrade of buildbot.python.org from Buildbot 0.8.x to 0.9.x,
the xmlrpc interface has been removed.  This test is now skipped until
it can be rewritten to query a suitable substitute.

See PEP 539 for details.

Highlights of changes:

- Add Thread Specific Storage (TSS) API
- Document the Thread Local Storage (TLS) API as deprecated
- Update code that used TLS API to use TSS API

There just isn't much we can assert in a portable way.

Per PEP 492, 'async' and 'await' should become proper keywords in 3.7.

Implement PEP 553, built-in breakpoint() with support from sys.breakpointhook(), along with documentation and tests.  Closes bpo-31353

Fix test_exception_errpipe_bad_data() and
test_exception_errpipe_normal() of test_subprocess: mock os.waitpid()
to avoid calling the real os.waitpid(0, 0) which is an unexpected
side effect of the test.

sre_compile does bit test (e.g. `flags & SRE_FLAG_IGNORECASE`) in loop.
`IntFlag.__and__` and `IntFlag.__new__` made it slower.

So this commit convert it to normal int before passing flags to `sre_compile()`.