commit (head): merge documents stuff

This is some preliminary stuff for a new implementation of the Merge
Documents feature. The new implementation will be using XyDiff algorithm
for the merging, which works much better (faster and with better
results) if the document elements use a unique id attribute 'xid'.
Because this attribute is unique it cannot be part of our normal
Attribute/Property mechanism (it would make every AP unique), and this
requires some adjustments to the PT and AW importer and exporter.

Start of the algorithm itself is in pd_XyDiff.h/cpp; this is in early
stage and is not included in the build system for now.

Modified files: many in ut, xap and ptbl, wp/impexp

Tomas
Received on Mon Jan 3 12:14:15 2005