In other news, I am aware of the expat-2.0 release, but this has a couple of API changes (and a new major library number) and it will take some time for upstream sources to patch for it. Therefore, expat-2.0 will not be used for Slackware 11.0 (but might be included in /testing).
I considered using --prefix=/usr here since X.Org will be moving from /usr/X11R6 to /usr when Slackware absorbs the modular release, but I think it will be best to wait and make those changes all at once. This, BTW, will be sometime after the 11.0 release. This current to stable cycle has already taken too much time (10.2 is in need of replacement), and introducing changes that might break things at this point would be foolhardy. Although there's still quite a bit in the TODO queue here I'm making my steps carefully as -current is very stable, and I think it should ship as a stable 11.0 soon so that we can get back to the business of breaking things in -current. :-)