If we're speaking of libxcb-util.so, this is in the libxcb extension, so only the relevant dep file(s) would need adjusting.
By that, do you mean that the files and libraries in libxcb-util were merged into the current libxcb.tcz package?
I tried transplanting some packages from Core 5.x and 4.x into my system, but I got frustrated and couldn't to get it to work yet. There are quite a few other missing packages and a version conflict with libgcrypt (It expects the one from Core 5.x). I'm really not a fan of mixing package versions, so I'll try building from source against the current Core 6.x libraries and see if I can create a working tcz package.
That being said, I think packages should only be included in the repository if they've been tested as installable and working. Including old, broken packages just annoys people.