In order support the possiblity for having multiple alternative
masters for the binlog server, we need to have multiple configs
around.
Originally the config values were stored as 'char *':s, which
would have made the lifetime management of the strings laborious
and error prone.
Now, the options are stored as std::string:s, which makes the
lifetime management a non-issue.
When receiving a command, such as
CHANGE MASTER TO MASTER_HOST = '127.0.0.1' ...
when the value is extracted, the quotes are removed before the value
is returned.
Firstly, BLR does not anyway anywhere enforce that quotes are present
where they should be and, secondly, BLR currently does de-quoting all
over the place and with this change, all those places can be simplified.
The configuration system that modules use allows the SSL parameter
validation to be simplified. It should also provide more consistent error
messages for similar types of errors.
The SSL_LISTENER initialization is now done in one step. There was no good
reason to do it in two separate steps for listeners but in one step for
servers.
The `ssl` parameter now also accepts boolean values. As the parameter
behaves like a boolean and looks like a boolean, it ought to be a
boolean. It still accepts the custom `required` and `disabled` values
simply for backwards compatibility.
Also added the missing freeing functions for the SSL_LISTENER type. This
prevents failed SSL_LISTENER creations from leaking memory.
