patch 8.2.2645: using inline function is not properly tested

Problem:    Using inline function is not properly tested.
Solution:   Add test cases, esp. for errors.  Minor code improvements.
diff --git a/src/version.c b/src/version.c
index 6fda8fc..9b21d12 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2645,
+/**/
     2644,
 /**/
     2643,