As of now it’s not necessary to patch mplayer for vdpau anymore.
I’ve just updated my mplayer with ‘svn up‘ to revision number 28699, and saw, that a new switch was added to the official mplayer subversion branch 🙂 :

./configure --help | grep -i vdpau
--enable-vdpau enable VDPAU acceleration [autodetect]

So no more patching is needed anymore. You can even leave out the switch, because it’s set to ‘[autodetect]‘. This will only be used of course, if you have Nvidia’s vdpau drivers installed. At the moment driver version 180.29 works fine for me here, and it’s also available from this experimental repository [1].