updated for version 7.3.970

Problem:    Syntax highlighting can be slow.
Solution:   Include the NFA regexp engine.  Add the 'regexpengine' option to
            select which one is used. (various authors, including Ken Takata,
            Andrei Aiordachioaie, Russ Cox, Xiaozhou Liua, Ian Young)

src/structs.h

@@ -63,15 +63,16 @@ typedef struct growarray
 
 #define GA_EMPTY    {0, 0, 0, 0, NULL}
 
-/*
- * This is here because regexp.h needs pos_T and below regprog_T is used.
- */
-#include "regexp.h"
-
 typedef struct window_S		win_T;
 typedef struct wininfo_S	wininfo_T;
 typedef struct frame_S		frame_T;
 typedef int			scid_T;		/* script ID */
+typedef struct file_buffer	buf_T;  /* forward declaration */
+
+/*
+ * This is here because regexp.h needs pos_T and below regprog_T is used.
+ */
+#include "regexp.h"
 
 /*
  * This is here because gui.h needs the pos_T and win_T, and win_T needs gui.h
@@ -526,8 +527,6 @@ typedef struct
 # endif
 } cmdmod_T;
 
-typedef struct file_buffer buf_T;  /* forward declaration */
-
 #define MF_SEED_LEN	8
 
 struct memfile