fix wallet2::check_tx_hey_helper

And fix compilation bug in wallet_tx_builder and reorganize unit tests.

tests/unit_tests/CMakeLists.txt

@@ -95,6 +95,7 @@ set(unit_tests_sources
   test_peerlist.cpp
   test_protocol_pack.cpp
   threadpool.cpp
+  tx_construction_helpers.cpp
   tx_proof.cpp
   hardfork.cpp
   unbound.cpp