The user-space driver interface for the Nouveau driver has been changed (with a version bump to 0.0.16). The DRM code as well as libdrm needs to be updated against the latest Git head for it to work with the xf86-video-nouveau driver Git code. Multiple ioctls have been removed from the Nouveau driver and superseded by a new ioctl that allows multiple push buffers to be submitted and relocations to be applied on any buffer. There were also ioctls removed that were just needed for user-space mode-setting, since non-KMS support is being dropped. Thankfully the Nouveau driver is considered a staging driver in the Linux 2.6.33 kernel. The updated DRM for Nouveau should be pulled with the Linux 2.6.34 kernel.
The commit that changes the Nouveau interface and bumps the version can be found in this Git commit.