Fix issue 505 by updating abiMapping with result from constructor

[erivas]

Note: adding a test for this would need Solidity 0.6.x (see #383)

[ggrieco-tob]

Is this patch complete? It seems it will be necessary to correct the bytecode in case we load raw transactions here:

echidna/lib/Echidna/RPC.hs

Lines 96 to 111 in 673aece

	-- | Takes a list of Etheno transactions and loads them into the VM, returning the
	-- | address containing echidna tests
	execEthenoTxs :: (MonadState x m, Has VM x, MonadThrow m, Has TxConf y, MonadReader y m, M.MonadFail m)
	=> [T.Text] -> Maybe Addr -> Etheno -> m (Maybe Addr)
	execEthenoTxs ts addr et = do
	setupEthenoTx et
	res <- liftSH exec
	g <- view (hasLens . propGas)
	case (res, et) of
	(Reversion, _) -> throwM $ EthenoException "Encountered reversion while setting up Etheno transactions"
	(VMFailure x, _) -> vmExcept x >> M.fail "impossible"
	(VMSuccess (ConcreteBuffer bc),
	ContractCreated _ ca _ _ _ _) -> do
	hasLens . env . contracts . at ca . _Just . contractcode .= InitCode ""
	liftSH (replaceCodeOfSelf (RuntimeCode bc) >> loadContract ca)
	og <- get

[ggrieco-tob]

Superseeded by #593 (but thanks for the PR, this was an interesting idea to consider)