Enable BIP30 for I0coin on 2013-08-23 0:00 UTC

BIP30 disallows duplicate (coinbase) transactions. Creating
a duplicate coinbase transaction destroys unspent coins from
the original coinbase transaction.
Enable BIP16 for I0coin on 2013-08-23 0:00 UTC

BIP16 is Pay to Script Hash (P2SH). Which may or may not
be useful in the future.
Stop enforcing BDB limits on 2013-08-23 0:00 UTC

Well, I0coin never reached those BDB limits, but since all
BDB based clients will disappear from the new chain, we
can safely drop compatibility kludges.
Don't enforce v2 blocks.

Version 2 blocks have their height encoded in the first 4 bytes of
the coinbase input script. getauxblock produces v1 blocks.

This can be enabled later if getauxblock is updated and most miners
produce v2 blocks. (desireable, but it won't cause a hard fork, since
95% of the miners automatically produce the best chain)
fix retarget at 890000

I0coins old retarget algorithm is asymmetric; difficulty decrease
is fast and difficulty increase is slow. This can be abused to
make a 51% attack more profitable than it should be (thereby
encouraging it).

This patch changes the retarget algorithm to be on par with
bitcoin's alogirithm (max factor of 4 every 2016 blocks).
Since i0coin retargets every 120 blocks, the actual retarget
factor is 4^(120/2016) = 1.086.

Use integer arithmetic, to make sure that all architectures
return the exact same answer.
Merge branches 'disregard_supermajority_v2_blocks', 'enable_BIP16_2013aug23', 'enable_BIP30_2013aug23', 'fix_retarget_at_890000' and 'lift_BDB_limits' into i0coin-0.8.x
Hardforking release candidate: 0.8.3-2rc1
Finalize date for hardfork

BIP16, BIP30 and dropping of BDB limits is moved to
2013-09-01 0:00 UTC. Difficulty algorithm is scheduled for
block 895000. Under normal circumstances this will happen
after 2013-09-01 (expected 29 days from now).
update version numbers to 0.8.3-2rc2
update version numbers to 0.8.3-2