patch 8.1.0684: warnings from 64-bit compiler

Problem:    Warnings from 64-bit compiler.
Solution:   Add type casts. (Mike Williams)
diff --git a/src/version.c b/src/version.c
index c337967..0493ec4 100644
--- a/src/version.c
+++ b/src/version.c
@@ -800,6 +800,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    684,
+/**/
     683,
 /**/
     682,