Move spacing code around (and fix a bug)

Move spacing code around (and fix a bug)

	* LaTeXFeatures.cpp (getPackages): remove some specific spacing code;
	move listings support to simplefeatures array.

	* src/Spacing.cpp (writeEnvirBegin, writeEnvirEnd): code factorization
	(writePreamble): new method containing former code from LaTeXFeatures;
	use \setSpacing instead of \setSingleSpacing.

	* src/BufferParams.cpp (validate, writeLaTeX): handle spacing here.

git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@22644 a592a061-630c-0410-9148-cb99ea01b6c8