nl_tokens: give child class a place to define its own methods
pl_tokens: function ctor ( ) { this . constructor = <mask> ; if ( MXI_DEBUG ) { var getCtorName = function ( fn ) { var m = fn . toString ( ) . match ( / ^function\s([^\(\s]+) / ) ; return m ? m [ 1 ] : false ; } ; this . ctorName = getCtorName ( child ) ; } }