Fix build with later WDKs

Fix build with later WDKs

- Adds alias for GetProjectInfoForReference target to version.vcxproj
    Later kits seemed to have renamed the build target, and will fail without
    this alias target.
- Adds "/fd sha256" to signtool command line
    WDK 20344 and later require binaries signed with a SHA256 file digest, or
    the build outputs are deleted

Signed-off-by: Owen Smith <owen.smith@citrix.com>
- Squash warnings 4061 (in xencons.vcxproj) and 26052 (in
  xencons_monitor.vcxproj) to avoid bogus noise.

Signed-off-by: Paul Durrant <paul@xen.org>