commit https://github.com/vim/vim/commit/b8060fe862f684b591f9ac679eac5b2594d6c5a0 Author: Bram Moolenaar <Bram@vim.org> Date: Tue Jan 19 22:29:28 2016 +0100 patch 7.4.1142 Problem: Cannot define keyword characters for a syntax file. Solution: Add the ":syn iskeyword" command. (Christian Brabandt)

--- a/src/structs.h
+++ b/src/structs.h
@@ -1362,6 +1362,8 @@ typedef struct {
 #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;