Process included files directly in the cross-referencer.
Process included files directly in the cross-referencer.

This fixes finding include files if include files include other files
and prepares for better handling of source-locations in included material.

koryonik/swipl-devel,edechter/swipl-devel,jn7163/swipl-devel,mndrix/swipl-devel,koryonik/swipl-devel,mndrix/swipl-devel,edechter/swipl-devel,edechter/swipl-devel,edechter/swipl-devel,mndrix/swipl-devel,mndrix/swipl-devel,koryonik/swipl-devel,jn7163/swipl-devel,jn7163/swipl-devel,jn7163/swipl-devel,jn7163/swipl-devel,koryonik/swipl-devel,mndrix/swipl-devel,koryonik/swipl-devel,edechter/swipl-devel