From Nico Kruithof, "For the VNC server, it seems that the wrong include path is used. 

Instead of 
INCLUDE_DIRECTORIES(${LIBVNCCLIENT_INCLUDE_DIR})
the CMake variable 
INCLUDE_DIRECTORIES(${LIBVNCSERVER_INCLUDE_DIR})
should be used.

Attached is a fix for src/osgPlugins/vnc/CMakeLists.txt"