Cannot flick to the end of a horizontal ListView with LayoutMirroring

Cannot flick to the end of a horizontal ListView with LayoutMirroring

Forward port of fix for QTBUG-21756.
minXExtent calculated the offset due to highlight range incorrectly
(reversed) when mirroring enabled.  Also us same algorithm for fixup()
in GridView and ListView uses.

For QtQuick 2, this change also reverses the beginning and end highlight
range, as it should be, i.e. the preferredHighlightBegin is from the
right side in RightToLeft mode.  Also added snapping tests.

Task-number: QTBUG-21756
Change-Id: Ica0ba4ab5db0ce9c77f2da75e9f8293550bd37d1
Reviewed-by: Martin Jones <martin.jones@nokia.com>