It seems that the gm45-h264 branch of vaapi is not under active development - the tree hasn't been synced with the main tree since October 2012.
The best thing we can do is push upstream (Intel) to restart development on h264. I remember this to be a major selling point at the time for the X4500HD... It's a shame this is not implemented, as there are thousands of 4/5 year old laptops around still sporting this graphics card. Regards, Pedro