patch 8.2.3912: the ins_complete() function is much too long

Problem:    The ins_complete() function is much too long.
Solution:   Split it up into multiple functions. (Yegappan Lakshmanan,
            closes #9414)

src/version.c

@@ -749,6 +749,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    3912,
 /**/
     3911,
 /**/