patch 8.1.2408: syntax menu and build instructions outdated

Problem:    Syntax menu and build instructions outdated.
Solution:   Update build instructions and syntax menu.
diff --git a/src/version.c b/src/version.c
index 51f10a4..b8e4cf2 100644
--- a/src/version.c
+++ b/src/version.c
@@ -743,6 +743,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2408,
+/**/
     2407,
 /**/
     2406,