**Suggested by @cbeams:**
_includes/ref_block_chain.md:
* Mention that coinbase is the first transaction in a block.
**Suggested by @gmaxwell:**
_includes/ref_core_rpcs-abcdefg.md:
* Mention that you need to unlock your wallet when you run out of
keys in the keypool.
* Remove erroneous assertion that txindex=1 would allow
`getreceivedbyaddress` to check balances of addresses not
belonging to this wallet.
_includes/ref_transactions.md:
* Clarify that OP_RETURN scripts aren't usually executed because
they always return false.
en/developer-reference.md
* Add a warning about using block chain or mempool data in
executable context.
_includes/guide_wallets.md:
* Fix formula given for normal child key derivation to state that public
keys must also be provided to the HMAC hash function. This required
updating both text and images.
* Add one-paragraph warning about ancestor key compromise when the
ancestor extended public key is compromised along with a descended
private key. Update img/dev/en-hd-private-parent-to-private-child.*
to help illustrate this warning.
en/developer-reference.md:
* Remove %include% of previously-removed file which caused new versions
of Jekyll to die.
Thanks also (in alphabetical order) to @cbeams, @mikehearn, and
@tgeller, among others.
The last pre-squash commit was: c2b8d562aa107c7b68c60946cea14cdccc5159ad
