Skip directory symlinks in DOSFS_FindNextEx.

diff --git a/include/winnt.h b/include/winnt.h
index 67b50d6..60afdc4 100644
--- a/include/winnt.h
+++ b/include/winnt.h
@@ -2891,6 +2891,7 @@
 #define FILE_ATTRIBUTE_XACTION_WRITE    0x00000400L
 #define FILE_ATTRIBUTE_COMPRESSED       0x00000800L
 #define FILE_ATTRIBUTE_OFFLINE		0x00001000L
+#define FILE_ATTRIBUTE_SYMLINK		0x80000000L  /* Not in Windows API */
 
 /* File notification flags */
 #define FILE_NOTIFY_CHANGE_FILE_NAME    0x00000001