Merge pull request #6722

58254aa Fix stale comment in CTxMemPool::TrimToSize. (Matt Corallo)
2bc5018 Fix comment formatting tabs (Matt Corallo)
8abe0f5 Undo GetMinFee-requires-extra-call-to-hit-0 (Matt Corallo)
9e93640 Drop minRelayTxFee to 1000 (Matt Corallo)
074cb15 Add reasonable test case for mempool trimming (Matt Corallo)
d355cf4 Only call TrimToSize once per reorg/blocks disconnect (Matt Corallo)
794a8ce Implement on-the-fly mempool size limitation. (Matt Corallo)
e6c7b36 Print mempool size in KB when adding txn (Matt Corallo)
241d607 Add CFeeRate += operator (Matt Corallo)
e8bcdce Track (and define) ::minRelayTxFee in CTxMemPool (Matt Corallo)
9c9b66f Fix calling mempool directly, instead of pool, in ATMP (Matt Corallo)
49b6fd5 Add Mempool Expire function to remove old transactions (Pieter Wuille)
78b82f4 Reverse the sort on the mempool's feerate index (Suhas Daftuar)