Display version on minerd --help usage output.

cpu-miner.c

@@ -327,6 +327,7 @@ static void show_usage(void)
 {
 	int i;
 
+	printf("minerd version %s\n\n", VERSION);
 	printf("Usage:\tminerd [options]\n\nSupported options:\n");
 	for (i = 0; i < ARRAY_SIZE(options_help); i++) {
 		struct option_help *h;