G_FILE_ATTRIBUTE_DOS_IS_MOUNTPOINT allows mountpoints
(NTFS reparse points with IO_REPARSE_TAG_MOUNT_POINT tag) to
be told apart from symlinks (NTFS reparse points with
IO_REPARSE_TAG_SYMLINK tag), even though both are reported
by glib as "symlinks".

G_FILE_ATTRIBUTE_DOS_REPARSE_POINT_TAG allows the exact
reparse tag value to be obtained by the user. This way
even more exotic reparse points can be identified and
handled by the user (glib itself currently has no code
to work with any reparse points that are not symlinks
or mountpoints).