update mqttd main.c, fix debug with java bug for JSON with \0 bug

guowenxue

2019-08-03 1ba740d4f23b97f105bbc3dd9780904f422a766c

tools/rpi_crosstool.tar.bz2 does not exist in tree 5e7378725f9f4ed4516d254a29442c6e94fa9fc1