patch 9.1.0791: tests: errors in gen_opt_test.vim are not shown

Problem:  tests: errors in gen_opt_test.vim are not shown
Solution: update gen_opt_test.vim and write test.log,
          let the makefile output test.log (Milly)

closes: #15887

Signed-off-by: Milly <milly.ca@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/version.c b/src/version.c
index 89ca65c..c5d66b1 100644
--- a/src/version.c
+++ b/src/version.c
@@ -705,6 +705,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    791,
+/**/
     790,
 /**/
     789,