patch 8.2.0543: Vim9: function with varargs does not work properly

Problem:    Vim9: function with varargs does not work properly.
Solution:   Improve function type spec and add tests.  Fix bugs.
diff --git a/src/version.c b/src/version.c
index e85bc31..ae324b3 100644
--- a/src/version.c
+++ b/src/version.c
@@ -739,6 +739,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    543,
+/**/
     542,
 /**/
     541,