Security fixes (#48)

* unify tx versions; add missing protocol tx checks

* fixed errors with protocol_tx handling pre-Carrot

* fixed error caused by setting coinbase_tx version to 4

* fix eph pubkey check for protocol tx verification

* Update tx_pool.cpp

---------

Co-authored-by: Some Random Crypto Guy <somerandomcryptoguy@protonmail.com>
Co-authored-by: somerandomcryptoguy <139346562+somerandomcryptoguy@users.noreply.github.com>

src/cryptonote_basic/cryptonote_format_utils.cpp

@@ -1383,7 +1383,7 @@ namespace cryptonote
     {
       if (hf_version >= HF_VERSION_CARROT)
       {
-        // from v11, require outputs be carrot outputs
+        // from v10, require outputs be carrot outputs
         CHECK_AND_ASSERT_MES(o.target.type() == typeid(txout_to_carrot_v1), false, "wrong variant type: "
           << o.target.type().name() << ", expected txout_to_carrot_v1 in transaction id=" << get_transaction_hash(tx));
       } else {