make uninstall leaving include dir installed

[strk]

We used to have a special section for the include dir in 3.12 branch, so that after a default-configured make uninstall and make uninstall pair you'd get no ‘/usr/local/include/geos/’: No such file or directory

That section is now gone from 3.13 onward so while the files are removed, a tree of empty directories remains.

See also GH-1187