C++: Support destroying deletes

cpp/ql/lib/semmlecode.cpp.dbscheme

@@ -1365,6 +1365,8 @@ funbind(
 @assign_expr = @assignexpr | @assign_op_expr | @blockassignexpr
 
 /*
+  Binary encoding of the allocator form.
+
   case @allocator.form of
     0 = plain
   | 1 = alignment
@@ -1383,11 +1385,13 @@ expr_allocator(
 );
 
 /*
+  Binary encoding of the deallocator form.
+
   case @deallocator.form of
     0 = plain
   | 1 = size
   | 2 = alignment
-  | 3 = size_and_alignment
+  | 4 = destroying_delete
   ;
 */