DEFEATURE: pointer dereferencing for HashTable iterator

- this largely reverts 3f0f218d88 and 4ee65d12c4.

  Consistent addressing with support for wrapped pointer types (eg,
  autoPtr, std::unique_ptr) has proven to be less robust than desired.
  Thus rescind HashTable iterator '->' dereferencing (from APR-2019).

applications/test/HashTable3/Test-HashTable3.C

@@ -30,6 +30,7 @@ Description
 
 #include "argList.H"
 #include "HashTable.H"
+#include "HashPtrTable.H"
 #include "Map.H"
 #include "cpuTime.H"