Based on this discussion (https://www.mail-archive.com/dev@tomcat.apache.org/msg141233.htm) it seems that include/ and lib/ are unusable from outside, except the shared library. They serve no purpose for the outside world. As Rainer pointed out, they can savely be dropped. I will work on the change to leave them out during "make install".
Fixed in 1.2.24 and onwards.