In pydoc.py, the reference to Python' documentation was in http.
The link has been updated to use https.

* Fix typos
* Change warning text
* Add test

_PyUnicode_FromId() may return NULL.

Reported by coverity scan: CID 1426868, 1426867.

This is more complicated than it should be because we need to preserve the
useful mtime-based regeneration feature that lib2to3.pgen2.driver.load_grammar
has. We only look for the pickled grammar file with pkgutil.get_data and only if
the source file does not exist.

Skip the test which fails on FreeBSD with POSIX locale.

Skip the test to fix FreeBSD buildbots, until a fix can be found, so
the buildbots can catch other regressions.

Skip the test failing randomly because of known race condition.

Skip the test to fix macOS buildbots until a decision is made on the
proper fix for the race condition.

Add a new _Py_FindEnvConfigValue() function: code shared between
Windows and Unix implementations of _PyPathConfig_Calculate() to read
the pyenv.cfg file.

_Py_FindEnvConfigValue() now uses _Py_DecodeUTF8_surrogateescape()
instead of using a Python Unicode string, the Python API must not be
used early during Python initialization. Same change in Unix
search_for_exec_prefix(): use _Py_DecodeUTF8_surrogateescape().

Cleanup also encode_current_locale(): PyMem_RawFree/PyMem_Free can be
called with NULL.

Fix also "NUL byte" => "NULL byte" typo.

Replace Py_EncodeLocale() with _Py_EncodeLocaleRaw() in:

* _Py_wfopen()
* _Py_wreadlink()
* _Py_wrealpath()
* _Py_wstat()
* pymain_open_filename()

These functions are called early during Python intialization, only
the RAW memory allocator must be used.

Py_EncodeLocale() now uses _Py_EncodeUTF8_surrogateescape(), instead
of using temporary unicode and bytes objects. So Py_EncodeLocale()
doesn't use the Python C API anymore.

Closes bpo-15873.

* _Py_InitializeCore() doesn't call _PyMem_SetupAllocators() anymore
  if the PYTHONMALLOC environment variable is not set.
* pymain_cmdline() now sets the allocator to the default, instead of
  setting the allocator in subfunctions.
* Py_SetStandardStreamEncoding() now calls
  _PyMem_SetDefaultAllocator() to get a known allocator, to be able
  to release the memory with the same allocator.