Support all xymatrix arguments

Support all xymatrix arguments
	* src/LaTeXFeatures.C
	(LaTeXFeatures::getPackages): Add package xy

	* src/mathed/InsetMathXYMatrix.[Ch]
	(spacing_): New
	(spacing_code_): New
	(validate): New, require xy package

	* src/mathed/InsetMathXYMatrix.C
	(InsetMathXYMatrix::write): write spacing_ and spacing_code_
	(InsetMathXYMatrix::infoize): output spacing_ and spacing_code_

	* src/mathed/MathFactory.C
	(createInsetMath): handle special arguments of xymatrix

	* src/mathed/MathParser.C
	(Parser::parse1): ditto

git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@15643 a592a061-630c-0410-9148-cb99ea01b6c8