performance fix for return edges; if there were N start points (e.g. in a backwards analysis) and we did an unbalanced analysis, then the return-foe function was computed N times; now this is done only once
Merge branch 'feature/performance-fix-for-return-edges' into develop
adding synchronization on "val" due to possible race conditions (thanks to Damien Octeau for reporting this!)
incremental second phase (still buggy, though)
solver with both jumpSave and changedNodes
slow, but works
performance improvements