Increase length of benchmark strings

This is needed to avoid the compiler eliding the call in
highly-optimised builds.

benchmarks/matching_benchmarks.c

@@ -11,7 +11,7 @@
 #include <string.h>
 #include <sys/time.h>
 
-#define LEN 100
+#define LEN 1000
 #define RANGE_FIRST 'a'
 #define RANGE_LAST 'z'
 
@@ -31,9 +31,11 @@ static void matching_benchmark(const fsa_t *fsa)
 	for (int j = 0; j < LEN; ++j)
 		s[j] = CLAMP_CHAR(rand());
 
+	volatile bool match;
 	START_CLOCK();
-	fsa_accepts(fsa, s, LEN);
+	match = fsa_accepts(fsa, s, LEN);
 	STOP_CLOCK();
+	(void)match;
 }
 
 int main(void)