If FLAGS_2D_PROJECTION is set, the MVP matrices need updating when changing the viewport.

    f[2] = 0;   f[6] = 0;   f[10] = A;  f[14] = B;

    f[3] = 0;   f[7] = 0;   f[11] = 0;  f[15] = 1;

    c->transforms.dirty |= transform_state_t::VIEWPORT;

    if (c->transforms.mvp4.flags & transform_t::FLAGS_2D_PROJECTION)

        c->transforms.dirty |= transform_state_t::MVP;

}

// ----------------------------------------------------------------------------