Set Accept: application/bitcoin-paymentrequest header

Suggestion from BitPay: set an Accept: HTTP header when
fetching payment requests / payment ACKs.
Merge pull request #2944 from gavinandresen/acceptheader

Set Accept: application/bitcoin-paymentrequest header
Add protobuf 2.5.0 download to gitian release process
Qt 4.8.3 r2 in gitian and release process

Also needed to add `unzip` package for the added unzip command for
OpenSSL in the Qt build.
Make settxfee clear that units are btc/kb.
autotools: switch to autotools buildsystem
Merge pull request #2978 from gmaxwell/rpc_settxfee_doc

Make settxfee clear that units are btc/kb.
Bitcoin-Qt: Use qDebug() for printing to debug.log

- removes all usages of PrintDebugStringF from Qt code
- ensure same format for all debug.log messages "functionname : Message"
qt: add vout index to transaction id in transactions details dialog
Merge pull request #2973 from Diapolo/qDebug

Bitcoin-Qt: Use qDebug() for printing to debug.log
Merge pull request #2976 from laanwj/2013_09_txid_details

qt: add vout index to transaction id in transactions details dialog
Merge pull request #2943 from theuni/autotools-final

Autotools buildsystem
configure.ac: remove superfluous bracket

Reported-by: Cory Fields
Merge pull request #2977 from laanwj/2013_09_release_process_protobuf

Add protobuf 2.5.0 download to gitian release process
Merge pull request #2968 from TheBlueMatt/master

Don't warn about forks while fIsInitialDownload
Longer term workaround for chainstate corruption from negative versions.

This also makes negative transaction versions non-standard.

This avoids an issue triggered in block 256818 where transactions with
negative version numbers were incorrectly serialized into the UTXO set.

On restart nodes detect the inconsistency and refuse to start so long as
a block with these transactions is inside the self-consistency check
window, logging "coin database inconsistencies found". The software
recommends reindexing, but reindexing does not correct the problem.

This should be fixed by changing the chainstate serialization, but
working around it seems harmless for now because the version is not
used by any network rule currently.

A patch free workaround is to start with -checklevel=2 which skips
the consistency checks, but the IsStandard change is important for
miners in order to protect unpatched nodes.
fix some cosmetic glitches in the codebase

- rename URL into URI in paymentserver where correct
- add some missing Qt-coding-stuff in paymentserver
- change QSpinBox to QLineEdit as base for BitcoinAmountField in .ui files
  (as this is the result when converting the BAF back into base)
- remove some c_str() and replace with QString::fromStdString()
- remove several new-lines
- remove unneeded spaces
- indentation fixes
Merge pull request #2961 from Diapolo/cosmetic

fix some cosmetic glitches in the codebase
autotools: use an absolute path to test data
configure: Check common include subdirectories for bdb headers, and refuse to use any version other than 4.8 by default