Close, but no cigar :).  Posted Rietveld comments to address the last two compile issues (one of which also appears to be a major bug, but only a warning at compile time).

Also, Victor has added os.get_blocking() and os.set_blocking(), which prevent your patch from applying cleanly (I tested against the parent of Victor's changeset).

After fixing the two issues I pointed out on Rietveld, I still get major failure on test:

======================================================================
ERROR: test_1565150 (__main__.StatAttributeTests)
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Traceback (most recent call last):
  File "P:\ath\to\cpython\lib\test\test_os.py", line 214, in tearDown
    os.rmdir(support.TESTFN)
OSError: [WinError 145] The directory is not empty: '@test_13492_tmp'

======================================================================
ERROR: test_1686475, test_file_attributes, test_large_time, test_stat_attributes, test_stat_attributes_bytes, test_stat_result_pickle, test_utime, test_utime_dir, test_utime_invalid_arguments, test_utime_ns, test_utime_subsecond, test_exist_ok_existing_directory, test_exist_ok_existing_regular_file, test_exist_ok_s_isgid_directory, test_makedir (All the same error)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "P:\ath\to\cpython\lib\test\test_os.py", line ###, in setUp
    os.mkdir(support.TESTFN)
FileExistsError: [WinError 183] Cannot create a file when that file already exists: '@test_13492_tmp'

======================================================================
ERROR: test_urandom_fd_reopened (__main__.URandomTests)
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Traceback (most recent call last):
  File "P:\ath\to\cpython\lib\test\test_os.py", line 1138, in test_urandom_fd_reopened
    with open(support.TESTFN, 'wb') as f:
PermissionError: [Errno 13] Permission denied: '@test_13492_tmp'

======================================================================
FAIL: test_chdir (__main__.Win32ErrorTests)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "P:\ath\to\cpython\lib\test\test_os.py", line 1274, in test_chdir
    self.assertRaises(OSError, os.chdir, support.TESTFN)
AssertionError: OSError not raised by chdir

----------------------------------------------------------------------
Ran 164 tests in 5.122s

The problem appears to be in unlink or rmdir, but I can't see anything amiss in either one.  I'll keep looking, but you may have a better idea what's going wrong.