void enableSystemErr() {
        systemErrEnabled = true;
    }
Creates a new parser for a .def file with the given name and that can be accessed by the given reader.

@param name  The name of the .def file (not including the '.def' suffix).
@param defReader  A reader to the .def file.
configgen/src/main/java/com/yahoo/config/codegen/DefParser.java