cs: protect special filenames from directory-list

For example, return `\\?\REL\\aux` instead of `aux`.

racket/src/io/file/host.rkt

@@ -3,12 +3,14 @@
          "../path/complete.rkt"
          "../path/parameter.rkt"
          "../path/cleanse.rkt"
+         "../path/protect.rkt"
          "../host/rktio.rkt"
          "../security/main.rkt")
 
 (provide ->host
          ->host/as-is
-         host->)
+         host->
+         host-element->)
 
 ;; Note: `(host-> (->host x who flags))` is not the same as `x`, since
 ;; it normalizes `x`. That's why `(host-> (->host x))` is generally
@@ -31,3 +33,9 @@
 (define (host-> s)
   (path (bytes->immutable-bytes s)
         (system-path-convention-type)))
+
+(define (host-element-> s)
+  (if (eq? 'windows (system-path-convention-type))
+      (path (protect-path-element (bytes->immutable-bytes s) 'windows)
+            'windows)
+      (host-> s)))

racket/src/io/file/main.rkt

@@ -146,7 +146,7 @@
              [else
               (rktio_free fnp)
               (end-atomic)
-              (loop (cons (host-> fn) accum))]))])))))
+              (loop (cons (host-element-> fn) accum))]))])))))
 
 (define/who (delete-file p)
   (check who path-string? p)