Approx_ComputeCLine.gxx - criterium to stop interval cutting is increased.
ProjLib_ProjectedCurve.cxx - fix regression for bugs modalg_5 bug25886
Other tests are modified according to current state of algorithm
1. New testgrid "lowalgos/intss" has been created. It will contain all test cases on geometrical intersection of two surfaces ("intersect" DRAW-command) and two faces ("bopcurves" DRAW-command).
2. New test case for the issue #28493 has been created because the problem is not reproduced on MASTER.
3. Test case (lowalgos/intss/bug24472) for the issue #29501 has been modified in order to check loops of the resulting intersection curves.