Be more tolerant of certain autoconf-defined variables not being

available.

This can happen if needing to regenerate the autoconf goop on an
older system (such as CentOS 6), where PACKAGE_URL doesn't get
defined.

src/locale.c

@@ -133,8 +133,12 @@ const char usage_longstr[] = "Usage: iperf [-s|-c host] [options]\n"
 			   "\n"
                            "[KMG] indicates options that support a K/M/G suffix for kilo-, mega-, or giga-\n"
 			   "\n"
+#ifdef PACKAGE_URL
                            "iperf3 homepage at: " PACKAGE_URL "\n"
+#endif /* PACKAGE_URL */
+#ifdef PACKAGE_BUGREPORT
                            "Report bugs to:     " PACKAGE_BUGREPORT "\n";
+#endif /* PACKAGE_BUGREPORT */
 
 
 #ifdef OBSOLETE /* from old iperf: no longer supported. Add some of these back someday */