[MERGE] Fast _walkdirs for win32

[Mark Hammond]

> it's defined outside of any other #if block. Actually comments say:
> 
> 	WINDOWS DEFINES:
> 	The code specific to Windows should be wrapped around one of
> 	the following #defines
> 
> 	MS_WIN64 - Code specific to the MS Win64 API
> 	MS_WIN32 - Code specific to the MS Win32 (and Win64) API
> (obsolete, this covers all 	supported APIs)
> 	MS_WINDOWS - Code specific to Windows, but all versions.
> 	MS_WINCE - Code specific to Windows CE
> 
> And the same comments explicitly called WIN32 symbol as deprecated:
> 
> 	NOTE: The following symbols are deprecated:
> 	NT, WIN32, USE_DL_EXPORT, USE_DL_IMPORT, DL_EXPORT, DL_IMPORT
> 	MS_CORE_DLL.
> 
> But I don't know in which Python version it was deprecated. May be Mark
> Hammond knows?

I can't recall the exact version, but I'm fairly sure it was a long long time ago - possibly back in the 1.x days, but way before 2.3.

Cheers,

Mark