d3d8types.h: Convert the D3DVSD_...SHIFT constants to unsigned.

[Gerald Pfeifer]

On Sat, 24 Oct 2015, Gerald Pfeifer wrote:
> This avoids potential shift overflows.  I only should be necessary
> for D3DVSD_TOKENTYPESHIFT, but it makes sense to have this consistent.

Correction, this per se does not avoid shift overflows, I sent an
older patch.  It still may make sense to apply (please advise), but
we'd need a different change in addition.  I'll have a look.

Gerald