Added printf format checking to logging function.

This also required changing the logging of "" at the
start of each test to appeal the otherwise-friendly
compiler.

test-tool/test_verify10_simple.c

@@ -31,7 +31,7 @@ test_verify10_simple(void)
 {
 	int i, ret;
 
-	logging(LOG_VERBOSE, "");
+	logging(LOG_VERBOSE, LOG_BLANK_LINE);
 	logging(LOG_VERBOSE, "Test VERIFY10 of 1-256 blocks at the end of the LUN");
 	for (i = 1; i <= 256; i++) {
 		unsigned char *buf = malloc(block_size * i);