tx: Add chainparams to struct bitcoin_tx as context

The way we build transactions, serialize them, and compute fees depends on the
chain we are working on, so let's add some context to the transactions.

Signed-off-by: Christian Decker <decker.christian@gmail.com>

common/initial_commit_tx.h

@@ -2,6 +2,7 @@
 #ifndef LIGHTNING_COMMON_INITIAL_COMMIT_TX_H
 #define LIGHTNING_COMMON_INITIAL_COMMIT_TX_H
 #include "config.h"
+#include <bitcoin/chainparams.h>
 #include <bitcoin/pubkey.h>
 #include <common/amount.h>
 #include <common/htlc.h>
@@ -52,6 +53,7 @@ static inline struct amount_sat commit_tx_base_fee(u32 feerate_per_kw,
 /**
  * initial_commit_tx: create (unsigned) commitment tx to spend the funding tx output
  * @ctx: context to allocate transaction and @htlc_map from.
+ * @chainparams: Params for the resulting transactions
  * @funding_txid, @funding_out, @funding: funding outpoint.
  * @funder: is the LOCAL or REMOTE paying the fee?
  * @keyset: keys derived for this commit tx.
@@ -69,6 +71,7 @@ static inline struct amount_sat commit_tx_base_fee(u32 feerate_per_kw,
  * transaction, so we carefully use the terms "self" and "other" here.
  */
 struct bitcoin_tx *initial_commit_tx(const tal_t *ctx,
+				     const struct chainparams *chainparams,
 				     const struct bitcoin_txid *funding_txid,
 				     unsigned int funding_txout,
 				     struct amount_sat funding,