patch 8.2.3022: available encryption methods are not strong enough

Problem:    Available encryption methods are not strong enough.
Solution:   Add initial support for xchaha20. (Christian Brabandt,
            closes #8394)
diff --git a/src/structs.h b/src/structs.h
index 26ab315..d62b10f 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -2513,11 +2513,12 @@
 # define CRYPT_M_ZIP	0
 # define CRYPT_M_BF	1
 # define CRYPT_M_BF2	2
-# define CRYPT_M_COUNT	3 // number of crypt methods
+# define CRYPT_M_SOD    3
+# define CRYPT_M_COUNT	4 // number of crypt methods
 
 // Currently all crypt methods work inplace.  If one is added that isn't then
 // define this.
-//  # define CRYPT_NOT_INPLACE 1
+# define CRYPT_NOT_INPLACE 1
 #endif
 
 #ifdef FEAT_PROP_POPUP