Fix assert to limit array size

CBMC has changed the representation of numerical values in
constant_expr (at least for array sizes) - instead of base 2, it now
uses base 16.

We have to fix this in our assertion that limits the size of arrays in
competition mode due to solver unsoundness that appears for arrays of
size >=50000.

Author: viktormalik

src/2ls/preprocessing_util.cpp

@@ -674,7 +674,7 @@ void twols_parse_optionst::limit_array_bounds(goto_modelt &goto_model)
           if(size_expr.id()==ID_constant)
           {
             int size=std::stoi(
-              id2string(to_constant_expr(size_expr).get_value()), nullptr, 2);
+              id2string(to_constant_expr(size_expr).get_value()), nullptr, 16);
             // @TODO temporary solution - there seems to be a bug in the solver
             assert(size<=50000);
           }