Problem - The default port number shown in SHOW SLAVE HOSTS is always 3306 
          though the slave is actually listening on a different port number.
          This is a problem as the user can not be sure whether this port 
          value can be trusted and so client trying to read replication 
          topology can get confused.

Fix - 3306 ceases to be the default value of report-port. Moreover report-port
      does not have a static default any longer.
      Instead we initialize report-port to 0 as the new default value and change
      it based on two checks :

      1) If report_port is not set, the slave reports the port number its listening 
         on. (i.e. if report-port is not set we get the actual value of the slave's 
         port number).

      2) If report-port is set, we show the value report-port is set to, as the slave's
         port number.

mysql-test/include/show_slave_hosts.inc:
  A .inc file is added to use show slave hosts in the new test added.
mysql-test/r/mysqld--help-notwin.result:
  Updated the result file to show the default value passed for report-port.
mysql-test/suite/rpl/r/rpl_report_port.result:
  The result file for the new test that is added.
mysql-test/suite/rpl/r/rpl_show_slave_hosts.result:
  Updated the result file to show the default value passed for report-port.
mysql-test/suite/rpl/t/rpl_report_port-slave.opt:
  Option file for the new test added.
mysql-test/suite/rpl/t/rpl_report_port.test:
  Added a test to check the correct functionality of report-port. 
  We check this by running the replication twice. 
          
  In the first run we do not set the value of report-port through the opt file 
  and get the actual port number of the slave's port.
          
  We then restart the server with report-port set to some value (in this case 9000)
  and check the value reported for the slave's port number.
mysql-test/suite/sys_vars/t/report_port_basic.test:
  Update the test file to show the value for report-port. It is replaced with
  SLAVE_PORT as the actual value of the report-port will change with each run.
sql/mysqld.cc:
  Changed the value reported by report port :
          
  1. If the value for report-port is not set we assign report-port to be the 
     actual port number of the slave (mysqld_port).
  
  2. If report-port is set we get the value set for the report-port.
sql/sys_vars.cc:
  Passed 0 as the default value of the report-port.