Fix for GetBlockValue() after block 13,440,000

Forces the block reward to zero when right shift in GetBlockValue() is
undefined, after 64 reward halvings (block height 13,440,000).
Fix importwallet nTimeFirstKey
gitian: add statically built variant of bitcoind/bitcoin-cli
remove an assignment which is never used.
unified and better log/error messages for CDBEnv/CDB
[Qt] rescan progress
Add gitian build guide

Work in progress...
Edit subsidy_limit_test to account for BIP42

Because no one wants 4 gold mines being discovered every mibillenium.
Merge pull request #3842 from ditto-b/master

Fix for GetBlockValue() after block 13,440,000
Merge pull request #3928

3927836 [Qt] rescan progress (Cozz Lovan)
Merge pull request #3998

cb4bdd1 Have pull-tester run the listtransactions.py regression test (Gavin Andresen)
Merge pull request #3929

4c35366 Fix importwallet nTimeFirstKey (Cozz Lovan)
Merge pull request #3994

2c47a00 Add gitian build guide (Wladimir J. van der Laan)
Merge pull request #3572

f7257cf unified and better log/error messages for CDBEnv/CDB (Philip Kaufmann)
Update README.md
Merge pull request #4005 from Telepatheic/patch-1

Update README.md
Move assert(pindexNew); to above where we dereference pindexNew.
Merge pull request #4010

94c8bfb Move assert(pindexNew); to above where we dereference pindexNew. (Gregory Maxwell)
Merge pull request #3972

fbf617a remove an assignment which is never used. (Yoichi Hirai)
Show error message if ReadConfigFile fails

A runaway exception was raised if ReadConfigFile fails (usually
due to a parse error in bitcoin.conf). Show an error message instead.

Fixes #4013.