Fix for internal forward references in PDF output (basic-link with internal-destination):

Fix for internal forward references in PDF output (basic-link with internal-destination):
Implemented by making out-of-order processing possible. The problem will still surface if supportsOutOfOrder() returns false.
PDF library now supports the addition of pages in non-consecutive order. This is a backwards-compatible change. The old behaviour and the old method signatures are still in place.
PageViewport now carries a page index which doesn't represent the page number but the overall index of the page within the current rendering run.

git-svn-id: https://svn.apache.org/repos/asf/xmlgraphics/fop/trunk@326133 13f79535-47bb-0310-9956-ffa450edef68