Prune provably-unspendable outputs
Use 'low S' as malleability breaker rather than 'even S'
Add michagogo to gitian download scripts
Adjust weight for michagogo in gitian download scripts

Following a discussion in #bitcoin-dev, around
19:00 UTC, 20132209
Merge pull request #3023 from Michagogo/pgp

Add michagogo to gitian download scripts
Merge pull request #3016 from sipa/lows

Use 'low S' as malleability breaker rather than 'even S'
Merge pull request #2791 from sipa/proveprune

Prune provably-unspendable outputs
Upgrade gitian win32 to Precise 12.04.

mingw upgrade allows more hardening, compiler bug fixes and possibily win64 later.
Rename deps .zip files to be more consistent in revision format.
Remove "msvc" compat triplet name.
LDFLAGS -static-libgcc -static-libstdc++
Upgrade win32 gitian to boost-1.54.0.
Workaround 1.54.0  build bug, upstream #9156
Workaround 1.54.0  build bug, binary-format=pe not auto-detected with target-os=windows
Workaround 1.51.0+ human bug, upstream dev refuses to include patch to allow cross-compile.