Bloodrayne: Terminal Cut (and Bloodrayne 2: Terminal Cut, and probably other
games in the series) streams from a SYSTEMMEM index buffer, updating it and
drawing from it every frame. This is currently slow on Wine, since each map
needs to wait for the previous upload (on the CS) to complete.

There are a few ways to avoid waiting, but this patch takes the approach of
effectively uploading from the SYSTEMMEM buffer on the client side, while using
a dynamic buffer to avoid client/CS synchronization. This brings performance
from 20-30 FPS to a (locked) 60, on NVidia GL drivers.