windows: Support all REPARSE_POINT attrib files properly. (#4203)

This change adopts the upstream fix in this regard at
https://go-review.googlesource.com/#/c/41834/ for Minio's
purposes.

Go's current os.Stat() lacks support for lot of strange
windows files such as

 - share symlinks on SMB2
 - symlinks on docker nanoserver
 - de-duplicated files on NTFS de-duplicated volume.

This PR attempts to incorporate the change mentioned here

   https://blogs.msdn.microsoft.com/oldnewthing/20100212-00/?p=14963/

The article suggests to use Windows I/O manager to
dereference the symbolic link.

Fixes #4122

cmd/posix-list-dir-others.go

@@ -55,7 +55,7 @@ func readDir(dirPath string) (entries []string, err error) {
 			// Stat symbolic link and follow to get the final value.
 			if fi.Mode()&os.ModeSymlink == os.ModeSymlink {
 				var st os.FileInfo
-				st, err = os.Stat(preparePath(path.Join(dirPath, fi.Name())))
+				st, err = osStat(preparePath(path.Join(dirPath, fi.Name())))
 				if err != nil {
 					errorIf(err, "Unable to stat path %s", path.Join(dirPath, fi.Name()))
 					continue