[antlr-interest] Commented-Out references to missing rule return values cause syntax errors

[Douglas Godfrey]

The following line generates an error in Antlr even though it is commented out.

//pNodeList -> push_back($range_test.pXmlNode);


range_test[std::string name, XmlNode * pParentNode]
	:	Range
		{TRACERULE(-1);}
		LParen
		{TRACERULE(-1);}
		(	(constant_expression Comma
constant_expression)=>(constant_expression Comma constant_expression)
		|	condition_expression[$pParentNode]
		)
		RParen
		{TRACERULE(-1);}
	;


robotC_Parser.g:294:4: unknown attribute for rule range_test: pXmlNode