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.

end:
2:1
2:17
2:20
3:1
3:17
3:20
5:8
5:25
5:28
6:8
6:25
6:28
8:1
8:9
8:17
8:25
8:27
9:1
9:9
9:17
9:25
9:26
9:26
9:1
9:9
9:17
9:25
9:26