examples: fix 3 compiler warnings

examples: fix 3 compiler warnings

examples/hotplugtest.c:76:28: warning: implicit conversion loses integer precision: 'long' to 'int' [-Wshorten-64-to-32]
        vendor_id  = (argc > 1) ? strtol (argv[1], NULL, 0) : 0x045a;
                   ~              ^~~~~~~~~~~~~~~~~~~~~~~~~
examples/hotplugtest.c:77:28: warning: implicit conversion loses integer precision: 'long' to 'int' [-Wshorten-64-to-32]
        product_id = (argc > 2) ? strtol (argv[2], NULL, 0) : 0x5005;
                   ~              ^~~~~~~~~~~~~~~~~~~~~~~~~
examples/hotplugtest.c:78:28: warning: implicit conversion loses integer precision: 'long' to 'int' [-Wshorten-64-to-32]
        class_id   = (argc > 3) ? strtol (argv[3], NULL, 0) : LIBUSB_HOTPLUG_MATCH_ANY;
                   ~              ^~~~~~~~~~~~~~~~~~~~~~~~~