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 1.51.0+ human bug, upstream #7262

Upstream 1.51.0 fixed a multiple reference bug that is problematic with the new mingw g++.  Upgrading boost seemed like a good idea but it introduced other build issues.  The cross-compile patch is by the Fedora package developer and shipped in Fedora.