updated for version 7.4.399

Problem:    Encryption implementation is messy.  Blowfish encryption has a
            weakness.
Solution:   Refactor the encryption, store the state in an allocated struct
            instead of using a save/restore mechanism.  Introduce the
            "blowfish2" method, which does not have the weakness and encrypts
            the whole undo file. (largely by David Leadbeater)

src/structs.h

@@ -1251,6 +1251,24 @@ typedef struct {
 } syn_time_T;
 #endif
 
+#ifdef FEAT_CRYPT
+/*
+ * Structure to hold the type of encryption and the state of encryption or
+ * decryption.
+ */
+typedef struct {
+    int	    method_nr;
+    void    *method_state;  /* method-specific state information */
+} cryptstate_T;
+
+/* values for method_nr */
+# define CRYPT_M_ZIP	0
+# define CRYPT_M_BF	1
+# define CRYPT_M_BF2	2
+# define CRYPT_M_COUNT	3 /* number of crypt methods */
+#endif
+
+
 /*
  * These are items normally related to a buffer.  But when using ":ownsyntax"
  * a window may have its own instance.
@@ -1778,7 +1796,12 @@ struct file_buffer
     int		b_was_netbeans_file;/* TRUE if b_netbeans_file was once set */
 #endif
 
-};
+#ifdef FEAT_CRYPT
+    cryptstate_T *b_cryptstate;	/* Encryption state while reading or writing
+				 * the file. NULL when not using encryption. */
+#endif
+
+}; /* file_buffer */
 
 
 #ifdef FEAT_DIFF