Fix for memory leaks when creating and destroying yajl objects.

I noticed some memory leaks when testing a Tcl program using yajl-tcl to parse large volumes of JSON data.

* When creating a yajl object using #auto for the command name,
  the auto-generated command name was not being freed.
* When destroying a yajl object, the clientData structure was not
  being freed.
* When destroying a yajl object, the parser was not being freed.