Drop fees by 10x due to the persistently higher exchange rate.

The last fee drop was by 5x (from 50k satoshis to 10k satoshis)
in the 0.8.2 release which was about 6 months ago.

The current fee is (assuming a $500 exchange rate) about 5 dollar
cents. The new fee after this patch is 0.5 cents.

Miners who prefer the higher fees are obviously still able to
use the command line flags to override this setting. Miners who
choose to create smaller blocks will select the highest-fee paying
transactions anyway.

This would hopefully be the last manual adjustment ever required
before floating fees become normal.
Adds additional zero checks for setCompact
 These encoded values should all decode to zero

   Positive Numbers
    0x01003456 (1 byte  0x00)
    0x02000056 (2 bytes 0x0000)
    0x03000000 (3 bytes 0x000000)
    0x04000000 (4 bytes 0x000000_00)

   Negative Numbers
    0x00923456 -(0 bytes, so zero)
    0x01803456 -(1 byte  0x00)
    0x02800056 -(2 bytes 0x0000)
    0x03800000 -(3 bytes 0x000000)
    0x04800000 -(4 bytes 0x000000_00)
Don't store or send side-chain blocks lower than last checkpoint.
small changes to rpc command help message strings
build: Make sure historical release notes end up in distributions

Adds the historical release notes to release tarballs and windows
installers.
Limit the number of orphan blocks

In case the total number of orphan blocks in memory exceeds a limit
(currently set to 750), a random orphan block (which is not
depended on by another orphan block) is dropped. This means it will
need to be downloaded again, but it won't consume memory until then.
[Qt] Improve single step in bitcoinamountfield
gitian: Make linux build of OpenSSL deterministic

OpenSSL was embedding a timestamp causing its build to be
non-deterministic.
Change deps-linux to be deterministic by using FAKETIME
as needed and disabling it when it gets in the way.
gitian: Make linux boost dependency completely deterministic

It appears that the output was different every time.

This doesn't affect the final bitcoind/bitcoin-qt, but is confusing
nevertheless.

Fix it by using FAKETIME and zipping files in deterministic order.
Update the address for downloading libpng

The FTP server what we get libpng from only keeps the latest version in its main folder. Older versions are in the "history" folder. Apparently version 1.6.9 has been released, so 1.6.8 has moved to the history folder.
Merge pull request #3635

12edce5 Update the address for downloading libpng (Micha)
Merge pull request #3608

de21e8f build: Make sure historical release notes end up in distributions (Wladimir J. van der Laan)
[Qt] remove broken OptionsModel::Upgrade()
remove setting methods in wallet/walletdb
doc: add preliminary release notes for 0.9.0
gitian: Make windows dependencies outputs fully deterministic

Sort .zip order, and other determinism changes to make sure builds
are repeatable for windows deps.
Cleanup v0.9 release notes
Merge pull request #3642 from petertodd/v0.9-release-notes-formatting-fixes

v0.9 release notes formatting fixes
Merge pull request #3609 from sipa/limitorphanblocks

Limit the number of orphan blocks in memory
Per-peer block download tracking and stalled download detection.

Keep track of which block is being requested (and to be requested) from
each peer, and limit the number of blocks in-flight per peer. In addition,
detect stalled downloads, and disconnect if they persist for too long.

This means blocks are never requested twice, and should eliminate duplicate
downloads during synchronization.