Configuring MySQL slave to use SSL
Older versions of MySQL allow declaring the CHANGE MASTER TO parameters in my.cnf. Newer version may not. In fact, according to the MySQL Documentation concerning setting replication options in my.cnf:


  Before MySQL 5.1.17, these options are silently ignored if given
  unless there is no master.info file. If that file exists, the MySQL
  server has already previously been configured for replication, so the
  information in the file is used instead. Because the server gives an
  existing master.info file precedence over the startup options just
  described, you might elect not to use startup options for these values
  at all, and instead to specify the replication parameters associated
  with them by using the CHANGE MASTER TO statement. See Section
  12.5.2.1, “CHANGE MASTER TO Syntax”. 
  
  Beginning with MySQL 5.1.17, these options are deprecated and have no
  effect when mysqld is started. If they are used, an appropriate
  warning is written to the error log. Instead, you must use CHANGE
  MASTER TO to set the values corresponding to the deprecated options.
  These options are removed in MySQL 5.5.


Naturally, running CHANGE MASTER TO generates a master.info file, which includes master_ssl. No harm, no foul. Relying on my.cnf for older versions of mysql results in option being ignored when no master.info exists. They are no longer valid.