Windows: fix syscall.ERROR_MORE_DATA

[neilalexander]

The syscall.ERROR_MORE_DATA code is not a true error condition on Windows and shouldn't be treated as such when performing reads/writes. This PR now correctly handles this condition, reading the rest of the available buffer before returning.

[Vort]

This fix may be not correct.

[neilalexander]

I'm actually not convinced it is anymore either. I think someone who knows Windows better than me should really take a look at this.

[songgao]

According to https://docs.microsoft.com/en-us/windows/win32/api/winreg/nf-winreg-regenumvaluea , ERROR_MORE_DATA seems to mean the data available for read is larger than the asked size, in this case I assume is the size of the buffer that's passed into the Read. If that's the case, it seem this error should just be returned and caller should use a buffer that's large enough.

[neilalexander]

I'm closing this PR because I am hopelessly useless with the Win32 API and I don't think this actually resolves the problem. I think you are perhaps right about input buffer sizes.