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