message: add some tracing to intptrcast
diff: @@ -90,6 +90,10 @@ impl<'mir, 'tcx> GlobalState {
  // From next_base_addr + slack, round up to adjust for alignment.
  let base_addr = Self::align_addr(global_state.next_base_addr + slack, align.bytes());
  entry.insert(base_addr);
  + trace!(
  + "Assigning base address {:#x} to allocation {:?} (slack: {}, align: {})",
  + base_addr, ptr.alloc_id, slack, align.bytes(),
  + );
  // Remember next base address. If this allocation is zero-sized, leave a gap
  // of at least 1 to avoid two allocations having the same base address.
  