Wiki would be good, and I agree with your comment about the formal docs, but where I think it really needs to go is in the INSTALL file. Lots of people are used to configure && make && make install, they are not so familiar with having to do the autoreconf -i.
Those who do a lott of svn/cvs-head building do know. It is very common.The INSTALL file also get's into the release, so that's not a good place, the wiki is.
