Reread number of columns, because after resize the number of childs is different

Changes

• Reread number of columns, because after resize the number of childs is different
• Add compile definition to enable blf tests

Conformity

• Changelog entry
• Downport

If external dependencies are removed

• Reporting to @scarlettmoore @jriddell The dbc parser was updated to upstream, because my changes were merged. It's basically the same, just a different remote now

Introduced with: b87ca47d