patch 9.0.1481: decrypting with libsodium may fail if the library changes

Problem:    Decrypting with libsodium may fail if the library changes.
Solution:   Add parameters used to the encrypted file header. (Christian
            Brabandt, closes #12279)
diff --git a/src/optionstr.c b/src/optionstr.c
index 8aec385..311b069 100644
--- a/src/optionstr.c
+++ b/src/optionstr.c
@@ -29,7 +29,7 @@
 #ifdef FEAT_CRYPT
 static char *(p_cm_values[]) = {"zip", "blowfish", "blowfish2",
  # ifdef FEAT_SODIUM
-    "xchacha20",
+    "xchacha20", "xchacha20v2",
  # endif
     NULL};
 #endif