[option] new value ordering heuristic exploiting last solution found (solution-based phase saving). see option -solr

[option trws] new option for TRW-S in preprocessing ; kill several bugs about ToulBar2::costMultiplier and check multiplication overflow when loading the problem

[bug] If an absolute gap is specified, only ub for true solutionsq/certificate can be shifted, niot initial Ubs.

      Warning: CUT, signature of endSolve() and ToulBar2::limited changed