Fix a typo in RPC signrawtransaction help
gitian: upgrade miniupnpc input to 1.9

Bumps deps-linux, deps-win dependency versions as well.

qt-win does not need to be bumped, as although it depends on deps-win,
Qt doesn't use miniupnp. I verified this by rebuilding the dependency
and checking the the output is the same. Not having to rebuild Qt is a
good thing as it is huge.
doc: update expected intermediate dependency hashes

Also move them to release-process.md from gitian-building.md for more
visibility.
Type-safe CFeeRate class

Use CFeeRate instead of an int64_t for quantities that are
fee-per-size.

Helps prevent unit-conversion mismatches between the wallet,
relaying, and mining code.
Save/restore the memory pool at shutdown/startup

Save the memory pool in a 'mempool.dat' file at shutdown, and
read it in at startup.
Allow multiple regression tests to run at once

Choose ports at startup based on PID, so multiple regression tests
can run on the same system at the same time.
Have pull-tester run listtransactions/mempool_save tests
estimatefee / estimatepriority RPC methods

New RPC methods: return an estimate of the fee (or priority) a
transaction needs to be likely to confirm in a given number of
blocks.

Mike Hearn created the first version of this method for estimating fees.
It works as follows:

For transactions that took 1 to N (I picked N=25) blocks to confirm,
keep N buckets with at most 100 entries in each recording the
fees-per-kilobyte paid by those transactions.

(separate buckets are kept for transactions that confirmed because
they are high-priority)

The buckets are filled as blocks are found, and are saved/restored
as part of the mempool.dat file.

A few variations on Mike's initial scheme:

To estimate the fee needed for a transaction to confirm in X buckets,
all of the samples in all of the buckets are used and a median of
all of the data is used to make the estimate. For example, imagine
25 buckets each containing the full 100 entries. Those 2,500 samples
are sorted, and the estimate of the fee needed to confirm in the very
next block is the 50'th-highest-fee-entry in that sorted list; the
estimate of the fee needed to confirm in the next two blocks is the
150'th-highest-fee-entry, etc.

That algorithm has the nice property that estimates of how much fee
you need to pay to get confirmed in block N will always be greater
than or equal to the estimate for block N+1. It would clearly be wrong
to say "pay 11 uBTC and you'll get confirmed in 3 blocks, but pay
12 uBTC and it will take LONGER".

A single block will not contribute more than 10 entries to any one
bucket, so a single miner and a large block cannot overwhelm
the estimates.