doc: update docs for Tor listening

- add new data directory files for 0.12 to doc/files.md
- mention torcontrol in doc/tor.md

Author: laanwj

doc/files.md

@@ -12,6 +12,8 @@
 * fee_estimates.dat: stores statistics used to estimate minimum transaction fees and priorities required for confirmation; since 0.10.0
 * peers.dat: peer IP address database (custom format); since 0.7.0
 * wallet.dat: personal wallet (BDB) with keys and transactions
+* .cookie: session RPC authentication cookie (written at start when cookie authentication is used, deleted on shutdown): since 0.12.0
+* onion_private_key: cached Tor hidden service private key for `-listenonion`: since 0.12.0
 
 Only used in pre-0.8.0
 ---------------------

doc/tor.md

@@ -87,3 +87,20 @@ If you only want to use Tor to reach onion addresses, but not use it as a proxy
 for normal IPv4/IPv6 communication, use:
 
 	./bitcoin -onion=127.0.0.1:9050 -externalip=57qr3yd1nyntf5k.onion -discover
+
+3. Automatically listen on Tor
+--------------------------------
+
+Starting with Tor version 0.2.7.1 it is possible, through Tor's control socket
+API, to create and destroy 'ephemeral' hidden services programmatically.
+Bitcoin Core has been updated to make use of this.
+
+This means that if Tor is running (and proper authorization is available),
+Bitcoin Core automatically creates a hidden service to listen on, without
+manual configuration. This will positively affect the number of available
+.onion nodes.
+
+This new feature is enabled by default if Bitcoin Core is listening, and
+a connection to Tor can be made. It can be configured with the `-listenonion`,
+`-torcontrol` and `-torpassword` settings. To show verbose debugging
+information, pass `-debug=tor`.