Fix getting model for object address (unsigned -> size_t)

Bug exhibited by cbmc-java/iterator2 when run with --object-bits 35

Author: peterschrammel

src/solvers/flattening/bv_pointers.cpp

@@ -601,7 +601,7 @@ exprt bv_pointerst::bv_get_rec(
   result.set_value(value);
 
   pointer_logict::pointert pointer;
-  pointer.object=integer2unsigned(binary2integer(value_addr, false));
+  pointer.object=integer2size_t(binary2integer(value_addr, false));
   pointer.offset=binary2integer(value_offset, true);
 
   // we add the elaborated expression as operand