Require at least 11 samples before giving fee/priority estimates.

And have wallet-created transactions go throught the fee-sanity-check
code path.

The wallet now uses the mempool fee estimator with a new
command-line option: -txconfirmtarget (default: 1) instead
of using hard-coded fees or priorities.

A new bitcoind that hasn't seen enough transactions to estimate
will fall back to the old hard-coded minimum priority or
transaction fee.

-paytxfee option overrides -txconfirmtarget.

Relaying and mining code isn't changed.

For Qt, the coin control dialog now uses priority estimates to
label transaction priority (instead of hard-coded constants);
unspent outputs were consistently labeled with a much higher
priority than is justified by the free transactions actually
being accepted into blocks.

I did not implement any GUI for setting -txconfirmtarget; I would
suggest getting rid of the "Pay transaction fee" GUI and replace
it with either "target number of confirmations" or maybe
a "faster confirmation <--> lower fee" slider or select box.

3f7a61fc Update Gitian Build guide to include OSX (Michael Ford)

9d5ad718 Fix formatting in release-process.md (Michael Ford)

Also add to HelpMessage() what specifications are valid.

Passes tests:

```
$ ./bitcoin-qt 'bitcoin:?r=http://www.example.com/'
.. fixed the original problem - this launches mainnet.

$ ./bitcoin-qt 'bitcoin:mngeNQbTKnmaMbx8EXCYdwUbnt9JJD52cC'
.. launches testnet

$ ./bitcoin-qt -testnet 'bitcoin:1NXXeQRyMFFFRfyUix2o7mk1vhvk2Nxp78'
.. sanity check - launches mainnet.
```

Fixes #4355. Closes #4411.

fda3fed1 libsecp256k1 integration (Pieter Wuille)
55668266 secp256k1: Add build-side changes for libsecp256k1 (Cory Fields)
b150b09e secp256k1: add libtool as a dependency (Cory Fields)

462ad223 Clean up release-process.md after OS X gitian changes (Micha)

Sorry, my own fault this time.

This is PR #4271, but with the changes to the descriptors, both the names of the
files and the names of the intermediate build artifact archives, removed.
This also closes #3775 if it goes in, because it covers the changes in
that PR.

Note: This is added to our existing automake targets rather than as a
libtool-style lib. The switch to libtool-style targets can come later if it
proves to not add any complications.

qt: Always log warning/error messages to debug.log

By changing the logging stream for warnings from qDebug to qWarning,
these will always be logged to debug.log.

More important messages should end up in the log no matter
if -debug=qt is set.

4aaa0178 rework help messages for fee-related options (Philip Kaufmann)

9a6497ed http to https, 2013 to 2014 (Trevin Hofmann)

This makes it possible to switch to a more efficient map type
without changing all occurences manually.

Merges half of #4413.

- also make comment about rc-files in clientversion.h generic

Merges #4429.

5d599212 add missing BOOST_FOREACH indentation in ThreadSocketHandler() (Philip Kaufmann)
9e9ca2b6 small cleanup of #ifdefs in BindListenPort() (Philip Kaufmann)

e35b37b1 RPC client: Simplify command line string-to-JSON-value conversion code (Jeff Garzik)

Merging #3883 broke the Qt5 build, define the color in the standard
way.

Relay and alert user to double spends

Add a skiplist to the CBlockIndex structure.

de79aaa7 Move non-trivial uint256.h methods to uint256.cpp (Pieter Wuille)

16f33f16 fix RPC error replies (kazcw)

This allows fast (O(log n)) access to far predecessor blocks.
Use it to speed up CChain::FindFork and CChain::GetLocator.

ffebc1be Update verify.sh script to point to bitcoin.org (Michael Ford)

Now that downloads are no longer hosted on Sourceforge, update the
script to retrieve the binaries and signature file from bitcoin.org.

After pull #4288, RPC messages indicating errors have a Content-Length unrelated
to their actual contents, rendering bitcoin-cli and curl unable to decode the
reply.

This patch sets the Content-Length field based on the actual content returned.

Additionally, pull #4288 clobbered the error descriptions provided in
ErrorReply, which bitcoin-cli relies upon; this patch moves #4288 http-error
descriptions to an HTTPError method, allowing HTTPReply to pass content on
unchanged.

675bcd58 Correct comment for 15-of-15 p2sh script size (Michael Ford)