patch 8.2.2594: alternate buffer added to session file even when it's hidden

Problem:    Alternate buffer added to session file even when it's hidden.
Solution:   Check the 'buflisted' option. (closes #7951)
diff --git a/src/version.c b/src/version.c
index 45973ea..f1b8232 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2594,
+/**/
     2593,
 /**/
     2592,