patch 7.4.1142
Problem:    Cannot define keyword characters for a syntax file.
Solution:   Add the ":syn iskeyword" command. (Christian Brabandt)
diff --git a/src/structs.h b/src/structs.h
index 5c65cc6..143d46d 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -1362,6 +1362,8 @@
 #if !defined(FEAT_SYN_HL) && !defined(FEAT_SPELL)
     int		dummy;
 #endif
+    char_u	b_syn_chartab[32];	/* syntax iskeyword option */
+    char_u	*b_syn_isk;		/* iskeyword option */
 } synblock_T;