patch 7.4.730
Problem:    When setting the crypt key and using a swap file, text may be
            encrypted twice or unencrypted text remains in the swap file.
            (Issue 369)
Solution:   Call ml_preserve() before re-encrypting.  Set correct index for
            next pointer block.
diff --git a/src/proto/memline.pro b/src/proto/memline.pro
index 62a3ce6..ff5d24a 100644
--- a/src/proto/memline.pro
+++ b/src/proto/memline.pro
@@ -1,6 +1,6 @@
 /* memline.c */
 int ml_open __ARGS((buf_T *buf));
-void ml_set_crypt_key __ARGS((buf_T *buf, char_u *old_key, int old_cm));
+void ml_set_crypt_key __ARGS((buf_T *buf, char_u *old_key, char_u *old_cm));
 void ml_setname __ARGS((buf_T *buf));
 void ml_open_files __ARGS((void));
 void ml_open_file __ARGS((buf_T *buf));