Make GetAvailableCredit run GetHash() only once per transaction.

This makes the first getbalance/getinfo 63x faster on my wallet.

(cherry picked from commit bitcoin/bitcoin@a60ab0ba89289433563c4c0993904acbca8c99ff)
Merge pull request #378 from leofidus/1.7-bitcoin3973

Make GetAvailableCredit run GetHash() only once per transaction.
adjust code to reflect higher dust limit of Dogecoin
Merge pull request #379 from leofidus/1.7-dust

adjust code to reflect higher dust limit of Dogecoin
set Dogecoin alert keys
Merge pull request #380 from leofidus/1.7-alert

set Dogecoin alert keys
Update the Gitian descriptors
Update windows setup script
Update gitian instructions for LXC
decrease minimum blockchain size to current dogecoin level
Fix typos in Gitian instructions
Merge pull request #381 from langerhans/1.7-gitian

Update Gitian descriptors for Dogecoin
Merge pull request #382 from leofidus/1.7-blockchainsize

decrease minimum blockchain size to current dogecoin level
Branding updates for Dogecoin
warning and documentation changes to match dogecoin fees
Merge pull request #384 from leofidus/1.7-fee

warning and documentation changes to match dogecoin fees
Merge pull request #383 from langerhans/1.7-branding

Branding updates for Dogecoin
Remove --disable-tests from Gitian descriptor
Fix configure.ac to allow Dogecoin named build.
Fix Gitian descriptor for installer copying

Of course I did miss THIS -.-