* cygheap.h (struct cwdstuff): Add dir member to store cwd handle.

(cwdstuff::get_handle): New method.
	* path.cc (cwdstuff::set): When doit is true, always try to get
	directory handle.  Fail if duplicating handle fails.  Store handle
	in dir.  Fix potential SEGV when setting drive_length.

winsup/cygwin/cygheap.h

@@ -223,9 +223,11 @@ struct cwdstuff
 {
   char *posix;
   UNICODE_STRING win32;
+  HANDLE dir;
   DWORD drive_length;
   static muto cwd_lock;
   char *get (char *, int = 1, int = 0, unsigned = CYG_MAX_PATH);
+  HANDLE get_handle () { return dir; }
   DWORD get_drive (char * dst)
   {
     cwd_lock.acquire ();