Try to make the meaning of platlibdir clear.  The previous wording could
be misinterpreted to suggest that it will be used to find all shared
libraries on the system, and not just Python extensions.  Furthermore,
it was unclear whether it affects third-party (site-packages) extensions
or not.  The new wording tries to make its dual purpose clear,
and provide the additional example of extensions in site-packages.
(cherry picked from commit 242d956)

Co-authored-by: Michał Górny <mgorny@gentoo.org>

Try to make the meaning of platlibdir clear.  The previous wording could
be misinterpreted to suggest that it will be used to find all shared
libraries on the system, and not just Python extensions.  Furthermore,
it was unclear whether it affects third-party (site-packages) extensions
or not.  The new wording tries to make its dual purpose clear,
and provide the additional example of extensions in site-packages.
(cherry picked from commit 242d956)

Co-authored-by: Michał Górny <mgorny@gentoo.org>

* 'master' of github.com:python/cpython: (497 commits)
  bpo-40061: Fix a possible refleak in _asynciomodule.c (pythonGH-19748)
  bpo-40798: Generate a different message for already removed elements (pythonGH-20483)
  closes bpo-29017: Update the bindings for Qt information with PySide2 (pythonGH-20149)
  bpo-39885: Make IDLE context menu cut and copy work again (pythonGH-18951)
  bpo-29882: Add an efficient popcount method for integers (python#771)
  Further de-linting of zoneinfo module (python#20499)
  bpo-40780: Fix failure of _Py_dg_dtoa to remove trailing zeros (pythonGH-20435)
  Indicate that abs() method accept argument that implement __abs__(), just like call() method in the docs (pythonGH-20509)
  bpo-39040: Fix parsing of email mime headers with whitespace between encoded-words. (pythongh-17620)
  bpo-40784: Fix sqlite3 deterministic test (pythonGH-20448)
  bpo-30064: Properly skip unstable loop.sock_connect() racing test (pythonGH-20494)
  Note the output ordering of combinatoric functions (pythonGH-19732)
  bpo-40474: Updated coverage.yml to better report coverage stats (python#19851)
  bpo-40806: Clarify that itertools.product immediately consumes its inpt (pythonGH-20492)
  bpo-1294959: Try to clarify the meaning of platlibdir (pythonGH-20332)
  bpo-37878: PyThreadState_DeleteCurrent() was not removed (pythonGH-20489)
  bpo-40777: Initialize PyDateTime_IsoCalendarDateType.tp_base at run-time (pythonGH-20493)
  bpo-40755: Add missing multiset operations to Counter() (pythonGH-20339)
  bpo-25920: Remove socket.getaddrinfo() lock on macOS (pythonGH-20177)
  bpo-40275: Fix test.support.threading_helper (pythonGH-20488)
  ...