Revision 278690

Bugzilla #36487:
Background images were incorrectly positioned in some absolute positioned blocks.
Some additional attributes output by the XMLRenderer.
Refactored the layout for e-g and i-f-o. Introduced common base classes for the
corresponding flow objects as well as the e-g and i-f-o LMs.
Fixed incorrectly applied margins on region-body when writing mode is not lr.
Fixed application of correct percent base for margins and extents on regions
when the reference orientation is 90 degrees.
Fixed incorrectly positioned regions when writing mode is different between the
simple-page-master setting and the setting on the region.
Several updates to the layout engine test cases.
Submitted by: Manuel Mall <mm.at.arcus.com.au>