Change the ECDSA signing to produce smaller signatures.

Bitcoin git/0.9 has had new signature code for a long time that produces
 smaller signatures. Making transactions smaller results in less
 fees.
CScript::IsUnspendable method

Upstream: ec84e81e8383b3b1e1ef4a6dbcb088193d8de5d7

Conflicts:
	src/core.h
Skip unspendable outputs in consistency check

Conflicts:
	src/core.h
Update Qt 4.8.3 download link

Conflicts:
	contrib/gitian-descriptors/README
Merge commit 'efde29e' into 0.8.x
Fix and improve release-process.md

This commit adds a step, which is to git checkout the version to be
built. This ensures that the gitian-descriptors for said version will be
the correct ones. In addition, it updates the links for several
dependencies, where the previously existing links were dead.

Conflicts:
	doc/release-process.md
Merge commit '71888bf' into 0.8.x

Conflicts:
	src/netbase.h
Update contrib/debian: proper desktop category and update changelog
Merge commit '3f8241c' into 0.8.x