Processing the D3DDP2OP_CLEAR DP2 Token

DirectX 8.0 introduces some changes to the required processing of the D3DDP2OP_CLEAR token. Specifically a new flag D3DCLEAR_COMPUTERECTS has been added to the dwFlags field of the D3DHAL_DP2CLEAR data structure. This new flag is only passed to the driver when a pure device type is being used (that is, D3DCREATE_PUREDEVICE was specified when creating the device and the driver exports the D3DDEVCAPS_PUREDEVICE device cap). Furthermore, this flag is never passed to non-DirectX 8.0 drivers and it is not specified by using the legacy Clear or Clear2 driver callbacks.