If you have those sources then you have them all, which means no one has packaged treecc for VL. You have a number of alternatives:
1) get a Slackware package (most of them work) from www.linuxpackages.net
. Then use the command "installpkg" to install it.
2) compile it from source code
3) do 2 above but use vpackager to actually create a package you can share with the VL community
4) put in a request for someone to package it for you in our new package requests forum
5) get an rpm and use rpm2tgz to convert it to Slackware. This is risky. The package may not work