#459007: merge info from PC/getpathp.c and using/windows.rst to document the forming of sys.path under Windows.

as (~0U) on NetBSD which was causing it to appear as -1 when used as
a signed int for _multprocessing.SemLock.SEM_VALUE_MAX.  This works
around the problem by substituting INT_MAX on systems where it appears
negative when used as an int.

Fix the test if the native filesystem encoding is not utf-8 (eg. cp1250 on
Windows).

 * Rename _PyImport_FindExtension() to _PyImport_FindExtensionUnicode():
   the filename becomes a Unicode object instead of byte string
 * Rename _PyImport_FixupExtension() to _PyImport_FixupExtensionUnicode():
   the filename becomes a Unicode object instead of byte string

 fixes for netbsd (and dragonflybsd?)

test_args_string() and test_call_string() create shell scripts including the
path to the Python executable: use surrogateescape to encode paths including
surrogate characters.

path value may be changed, so keep a copy in a new variable.

to support surrogate characters

_Py_char2wchar() callers usually need the result size in characters. Since it's
trivial to compute it in _Py_char2wchar() (O(1) whereas wcslen() is O(n)), add
an option to get it.

surrogate characters.

surrogate characters.

new test specific to unicode (non-ascii name and filename).

Fix my previous commit (r85569).

filenames encoded to the filesystem encoding with surrogateescape error handler
(to support undecodable bytes), instead of UTF-8 in strict mode.