dwTextureBlendCaps is overwritten later, and (potentially) uninitialized here.

All remaining uses are equivalent to "device->up_strided". (Which should of
course eventually go away as well.)

Strided draws don't use VBOs.

device_stream_info_from_declaration() no longer cares about
state->user_stream.

Since user pointer draws were removed, state->user_stream will only ever be
set for "strided" draws, and device_stream_info_from_declaration() is never
called for those.

We can use the same code for the Gallium and "classic" drivers, and the
classic drivers are no longer supported upstream anyway.