updated for version 7.3.1028

Problem:    New regexp performance: Copying a lot of position state.
Solution:   Only copy the sub-expressions that are being used.

src/regexp.h

@@ -87,6 +87,7 @@ typedef struct
     regprog_T		regprog;
     nfa_state_T		*start;
     int			has_zend;	/* pattern contains \ze */
+    int			nsubexp;	/* number of () */
     int			nstate;
     nfa_state_T		state[0];	/* actually longer.. */
 } nfa_regprog_T;