=head2 Whitespace handling

  stripspaces => 0
    (default) All whitespace should be preserved.

  stripspaces => 1
    remove the whitespace-only content preceeding a tag whose rule did not
	return anything in a way that would cause it to be added to parent's
	_content and whitespace between such a tag and the closing parent tag.
	This means that no whitespace will be removed before <foo> in
	"<bar>blah <foo x="y"/></bar>" but (if the rule for <foo> returns nothing
	or an even-numbered list of things to be added to the parent's %$attr)
	both whitespaces will be removed in "<bar>   <foo x="y">   </bar>".

  stripspaces => 2
    remove all whitespace before tags that do not add anything into parent's
	_content and before the closing tag.

  stripspaces => 3
    as => 2, plus trims the _content of tags and doesn't include the _content
	for tags like "<foo x="y"></foo>" and "<foo x="y">   </foo>".

  normalisespaces => 0
    do not do anything with multiple spaces in a row

  normalisespaces => 1
    collapse multiple spaces in a row to a single one