This reverts commit 0220b58917b5a979891b5765f6ac5095e0368489.

I completely misread https://www.python.org/dev/peps/pep-0418/#rationale
and the accuracy of monotonic() is *worse* on windows than time.time(),
which is bizarre.

Change-Id: I2d571e268a2051bea68736507773d3904403af9e

The internal clock used by the :class:`_pool.Pool` object is now
time.monotonic_time() under Python 3.  Under Python 2, time.time() is still
used, which is legacy. This clock is used to measure the age of a
connection against its starttime, and used in comparisons against the
pool_timeout setting as well as the last time the pool was marked as
invalid to determine if the connection should be recycled. Previously,
time.time() was used which was subject to inaccuracies as a result of
system clock changes as well as poor time resolution on windows.

Change-Id: I94f90044c1809508e26a5a00134981c2a00d0405

Add support to ``FETCH {FIRST | NEXT} [ count ] {ROW | ROWS}
 {ONLY | WITH TIES}`` in the select for the supported backends,
currently PostgreSQL, Oracle and MSSQL.

Fixes: #5576
Change-Id: Ibb5871a457c0555f82b37e354e7787d15575f1f7

It's better, the majority of these changes look more readable to me.
also found some docstrings that had formatting / quoting issues.

Change-Id: I582a45fde3a5648b2f36bab96bad56881321899b

Improved support for covering indexes (with INCLUDE columns). Added the
ability for postgresql to render CREATE INDEX statements with an INCLUDE
clause from Core. Index reflection also report INCLUDE columns separately
for both mssql and postgresql (11+).

Fixes: #4458
Change-Id: If0b82103fbc898cdaeaf6a6d2d421c732744acd6

This change includes mainly that the bracketed use within
select() is moved to positional, and keyword arguments are
removed from calls to the select() function.  it does not
yet fully address other issues such as keyword arguments passed
to the table.select().

Additionally, allows False / None to both be considered
as "disable" for all of select.correlate(), select.correlate_except(),
query.correlate(), which establishes consistency with
passing of ``False`` for the legact select(correlate=False)
argument.

Change-Id: Ie6c6e6abfbd3d75d4c8de504c0cf0159e6999108

Provide a default value for this requirement to expose it
to external dialects.

Change-Id: I3801a9134493efb65caa6793ef466a3cfb701592

Added support for direct mapping of Python classes that are defined using
the Python ``dataclasses`` decorator.    See the section
:ref:`mapping_dataclasses` for background.  Pull request courtesy Václav
Klusák.

Fixes: #5027
Closes: #5516
Pull-request: https://github.com/sqlalchemy/sqlalchemy/pull/5516
Pull-request-sha: bb48c63d1561ca48c954ad9f84a3eb2646571115

Change-Id: Ie33db2aae4adeeb5d99633fe926b9c30bab0b885