Change 'cryptmethod' from a number to a string option.  Make it global-local.
diff --git a/src/structs.h b/src/structs.h
index ebcc3cf..42b1d2a 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -1450,9 +1450,6 @@
 #ifdef FEAT_INS_EXPAND
     char_u	*b_p_cpt;	/* 'complete' */
 #endif
-#ifdef FEAT_CRYPT
-    long	b_p_cm;		/* 'cryptmethod' */
-#endif
 #ifdef FEAT_COMPL_FUNC
     char_u	*b_p_cfu;	/* 'completefunc' */
     char_u	*b_p_ofu;	/* 'omnifunc' */
@@ -1574,6 +1571,9 @@
     char_u	*b_p_bexpr;	/* 'balloonexpr' local value */
     long_u	b_p_bexpr_flags;/* flags for 'balloonexpr' */
 #endif
+#ifdef FEAT_CRYPT
+    char_u	*b_p_cm;	/* 'cryptmethod' */
+#endif
 
     /* When a buffer is created, it starts without a swap file.  b_may_swap is
      * then set to indicate that a swap file may be opened later.  It is reset