MSVC apparently 8-byte aligns 8-byte objects even in 32-bit builds so we need to use the 64-bit ABI to blkback/tap in all cases.
MSVC apparently 8-byte aligns 8-byte objects even in 32-bit builds
so we need to use the 64-bit ABI to blkback/tap in all cases.

Signed-off-by: Paul Durrant <dba6cd059c0054f8a3c62ba902cd9d7238853ee4@citrix.com>

xenserver/win-xenvbd,xenserver/win-xenvbd,xenserver/win-xenvbd