patch 8.1.2331: the option.c file is still very big

Problem:    The option.c file is still very big.
Solution:   Move a few functions to where they fit better. (Yegappan
            Lakshmanan, closes #4895)
diff --git a/src/version.c b/src/version.c
index 41bd4cc..db3a663 100644
--- a/src/version.c
+++ b/src/version.c
@@ -738,6 +738,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2331,
+/**/
     2330,
 /**/
     2329,