patch 9.0.1973: Clean up cmdline option completion code

Problem:  Clean up cmdline option completion code
Solution: Fix various minor problems

- Fix manual array size calculations to just use `ARRAY_LENGTH()`.
- Fix unintentional typo in comments due to copy-paste error.
- Fix assert_equal() usages to pass the expected value to first
  parameter instead of 2nd one to avoid confusion.
- Fix signed vs unsigned warnings
- Correct misplaced comments about set_op_T and set_prefix_T
  and fix a typo in another comment

closes: #13249
closes: #13237

Signed-off-by: Christian Brabandt <cb@256bit.org>
Co-authored-by: Yee Cheng Chin <ychin.git@gmail.com>
Co-authored-by: zeertzjq <zeertzjq@outlook.com>
diff --git a/src/version.c b/src/version.c
index 1eb6264..e93ee41 100644
--- a/src/version.c
+++ b/src/version.c
@@ -705,6 +705,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1973,
+/**/
     1972,
 /**/
     1971,