Throughout remove all usage of wincap.access_denied_on_delete.

* dir.cc (rmdir): Add existance check to be errno-compatible with Linux.
	* fhandler_disk_file.cc (fhandler_disk_file::rmdir): Drop test for
	non-existent dir on 9x share.
	* syscalls.cc (unlink): Add comment.
	* wincap.cc: Remove access_denied_on_delete flag throughout.
	* wincap.h: Ditto.

winsup/cygwin/dir.cc

@@ -309,6 +309,8 @@ rmdir (const char *dir)
     }
   else if (has_dot_last_component (dir, false))
     set_errno (fh->exists () ? EINVAL : ENOENT);
+  else if (!fh->exists ())
+    set_errno (ENOENT);
   else if (!fh->rmdir ())
     res = 0;