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)
(cherry picked from commit dogecoin/dogecoin@0fbd54e5cc5ce7f1ee51b11e3ebd5236f5f62450)
adjust code to reflect higher dust limit of Dogecoin

(cherry picked from commit dogecoin/dogecoin@c26327b8094cf94ba5948cd41f8220f4a8f2a313)
set Dogecoin alert keys

(cherry picked from commit dogecoin/dogecoin@380f4b0d2e589496cbef7644c5db662e926de7fd)
Updated Windows build guide with more realistic set of pre-requisites.

Updated libboost version listed in Windows build guide to match UNIX guide.
Rewrote libboost installation docs for Windows to match a more conventional process.

(cherry picked from commit dogecoin/dogecoin@87f8423a7c55431685297eae77b735c3f35ebb9f)
Change reference version of Berkeley DB to 5.1

This breaks forward compatibility of old clients. You can downgrade your wallet though with "db5.1_dump wallet.dat.old | db4.8_load wallet.dat"

(cherry picked from commit dogecoin/dogecoin@112c5c95a79b1a3883910f2710a9af9e1adf64f0)
Update the Gitian descriptors

(cherry picked from commit dogecoin/dogecoin@c0c746a84b146753e2ea099f4629ef1befd76149)
decrease minimum blockchain size to current dogecoin level

(cherry picked from commit dogecoin/dogecoin@65cff46af451cc203ef4bf587d7bdeb3b815fb67)
warning and documentation changes to match dogecoin fees

(cherry picked from commit dogecoin/dogecoin@9449d42332b450733298723b47df343a571e4f6b)
correct email in configure.ac
Merge branch 'master' of github.com:inutoshi/inutoshi

Conflicts:
	doc/build-unix.md
Added Dogechain to DNS seeds.

(cherry picked from commit dogecoin/dogecoin@44264855d056a307677952dbfe638b9f035f391a)