syscall: Windows Errno constants invalid

[networkimprov]

These constants: https://golang.org/src/syscall/types_windows.go#L7

Should appear in these constants: https://golang.org/src/syscall/zerrors_windows.go#L16

... because the latter are currently useless for comparison with Errno values, unlike other supported OSes. For example err.(*os.PathError).Err == syscall.ENOTEMPTY is never true on Windows.

Filed at request of @rsc

@gopherbot add OS-Windows

[rsc]

There do exist fake windows syscall Errnos. They won't go away entirely. But the fakes should only be used for traditional Unix errors that don't exist in Windows world. For example ENOENT and ENOTDIR already map to real windows errors instead of being provided by fakes. In the same way, ENOTEMPTY should map to ERROR_DIR_NOT_EMPTY. Perhaps there are others too. But to be clear, some (many) of the fakes will remain.

[networkimprov]

I'm unclear why each Errno that cannot appear on windows has a unique value. I would expect them to share a value, e.g. 0xbad5eed.

[networkimprov]

I think we're at NeedsFix here... Should this be assigned to someone?