Enable value-set to handle DEAD statements

The default behaviour is to ignore them, but value_sett now has the
opportunity to deal with them.

Author: smowton

src/pointer-analysis/value_set.cpp

@@ -1617,6 +1617,10 @@ void value_sett::apply_code_rec(
   {
     // doesn't do anything
   }
+  else if(statement==ID_dead)
+  {
+    // Ignore by default; could prune the value set.
+  }
   else
   {
     // std::cerr << code.pretty() << '\n';

src/pointer-analysis/value_set_domain_transform.inc

@@ -37,6 +37,7 @@ void value_set_domain_templatet<VST>::transform(
   case OTHER:
   case ASSIGN:
   case DECL:
+  case DEAD:
     value_set.apply_code(from_l->code, ns);
     break;