readdir() with mount point dentry, return mount point INO

readdir() with mount point dentry, return mount point INO

This patch fixes a minor compatibility issue w/ cygwin mount point handling in
readdir(), compared to equivalent behavior of Linux and MacOS. dentry.d_ino
should indicate the INO of the mount point itself, not the target volume root
folder.

Changed return type from readdir_check_reparse_point to uint8_t, to avoid
unnecessarily being implicitly cast to and from a signed int.

Renamed a related local variable "attr" to "oattr" that was eclipsing a member
variable with the same name.

Joe L.