doc: Update release notes for 0.12

Update and reword BIP 125 section

Mention changes to banlist (clearbanned/setban)

Pruning nodes can relay

doc/release-notes.md

@@ -104,6 +104,9 @@ announcing their headers directly, instead of just announcing the hash. In a
 reorganization, all new headers are sent, instead of just the new tip. This
 can often prevent an extra roundtrip before the actual block is downloaded.
 
+With this change, pruning nodes are now able to relay new blocks to compatible
+peers.
+
 Memory pool limiting
 --------------------
 
@@ -134,12 +137,32 @@ Replace-by-fee transactions
 ---------------------------
 
 It is now possible to replace transactions in the transaction memory pool of
-Bitcoin Core 0.12 nodes. Bitcoin Core will only replace transactions which
+Bitcoin Core 0.12 nodes. Bitcoin Core will only allow replacement of
-have any of their inputs' `nSequence` number set to less than `0xffffffff - 1`.
+transactions which have any of their inputs' `nSequence` number set to less
-Moreover, a replacement transaction may only be accepted when it pays
+than `0xffffffff - 1`.  Moreover, a replacement transaction may only be
-sufficient fee, as described in [BIP 125]
+accepted when it pays sufficient fee, as described in [BIP 125]
 (https://github.com/bitcoin/bips/blob/master/bip-0125.mediawiki).
 
+Transaction replacement can be disabled with a new command line option,
+`-permitrbf=false`.  Transactions signaling replacement under BIP125 will still
+be allowed into the mempool in this configuration, but replacements will be
+rejected.  This option is intended for miners who want to continue the
+transaction selection behavior of previous releases.
+
+The `-permitrbf` option is *not recommended* for wallet users seeking to avoid
+receipt of unconfirmed opt-in transactions, because this option does not
+prevent transactions which are replaceable under BIP 125 from being accepted
+(only subsequent replacements, which other nodes on the network that implement
+BIP 125 are likely to relay and mine).  Wallet users wishing to detect whether
+a transaction is subject to replacement under BIP 125 should instead use the
+updated RPC calls `gettransaction` and `listtransactions`, which now have an
+additional field in the output indicating if a transaction is replaceable under
+BIP125 ("bip125-replaceable").
+
+Note that the wallet in Bitcoin Core 0.12 does not yet have support for
+creating transactions that would be replaceable under BIP 125.
+
+
 RPC: Random-cookie RPC authentication
 ---------------------------------------
 
@@ -396,6 +419,14 @@ transaction's acceptance into the mempool and the mining code now relies on the
 consistency of the mempool to assemble blocks. However all blocks are still tested
 for validity after assembly.
 
+Other P2P Changes
+-----------------
+
+The list of banned peers is now stored on disk rather than in memory.
+Restarting bitcoind will no longer clear out the list of banned peers; instead
+a new RPC call (`clearbanned`) can be used to manually clear the list.  The new
+`setban` RPC call can also be used to manually ban or unban a peer.
+
 0.12.0 Change log
 =================