Multiple transactions per account in TxQ (RIPD-1048):

* Tweak account XRP balance and sequence if needed before preclaim.
* Limit total fees in flight to minimum reserve / account balance.
* LastLedgerSequence must be at least 2 more than the current ledger to be queued.
* Limit 10 transactions per account in the queue at a time.
* Limit queuing multiple transactions after transactions that affect authentication.
* Zero base fee transactions are treated as having a fixed fee level of 256000 instead of infinite.
* Full queue: new txn can only kick out a tx if the fee is higher than that account's average fee.
* Queued tx retry limit prevents indefinitely stuck txns.
* Return escalation factors in server_info and _state when escalated.
* Update documentation.
* Update experimental config to only include the % increase.
* Convert TxQ metric magic numbers to experimental config.

src/ripple/app/tx/impl/CreateOffer.cpp

@@ -32,6 +32,15 @@
 
 namespace ripple {
 
+XRPAmount
+CreateOffer::calculateMaxSpend(STTx const& tx)
+{
+    auto const& saTakerGets = tx[sfTakerGets];
+
+    return saTakerGets.native() ?
+        saTakerGets.xrp() : beast::zero;
+}
+
 TER
 CreateOffer::preflight (PreflightContext const& ctx)
 {