Extend win32 error codes to errno mapping in win32error.c

Hi,

I recently faced an issue on windows where one of the tests was
failing with 'unrecognized win32 error code: 123', see [1]. I figured
out that it was due to a wrong file name being sent to open() system
call (this error is of my own making and I fixed it for that thread).
The failure occurs in dosmaperr() in win32error.c due to an unmapped
errno for win32 error code. The error code 123 i.e. ERROR_INVALID_NAME
says "The file name, directory name, or volume label syntax is
incorrect." [2], the closest errno mapping would be ENOENT. I quickly
looked around for the other win32 error codes [2] that don't have
mapping. I filtered out some common error codes such as
ERROR_OUTOFMEMORY, ERROR_HANDLE_DISK_FULL, ERROR_INSUFFICIENT_BUFFER,
ERROR_NOACCESS. There may be many more, but these seemed common IMO.

Having a right errno mapping always helps recognize the errors correctly.

I'm attaching a patch that maps the above win32 error codes to errno
in win32error.c. I also think that we can add a note in win32error.c
by mentioning the link [2] to revisit the mapping whenever
"unrecognized win32 error code:XXX" error occurs.

Thoughts?

Thanks Michael Paquier for off list chat.

[1] https://www.postgresql.org/message-id/CALj2ACWKvjOO-JzYpMBpk-o_o9CeKGEqMcS=yXf-pC6M+jOkuQ@mail.gmail.com
[2] https://learn.microsoft.com/en-us/openspecs/windows_protocols/ms-erref/18d8fbe8-a967-4f1c-ae50-99ca8e491d2d

--
Bharath Rupireddy
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com