Listview: Improve performance

[gabrielschulhof]

• The list of anchors which is computed in the innermost loop is always reduced via .first(), even though in many cases there is only one anchor in the list. There is already special casing for when an li contains multiple anchors (split button), so we can improve the performance of all non-split-button-lists by avoiding an unnecessary call to .first()
• addFirstLastClasses() uses .not( ".ui-screen-hidden" ). This can be evaluated faster using a custom function that parses .className.