- Add two null bytes in  "buff" variable allowing us to call
   get_arg two times also for strings longer than sizeof(buff) 


client/mysql.cc:
  Make sure there are _two_ zero bytes at the end of buff, to allow 'get_arg' to be
  called twice on long strings. The first time it will mark end of string with a
  zero and the second time it will "skip ahead" to the first zero, and the find the
  second one indicating end of buff.
mysql-test/r/mysql.result:
  Update test results
mysql-test/t/mysql.test:
  Add tests for "com_connect" function in mysql
  Add test reported in bug