Fix fcl dependency in CMakeLists.txt

See http://answers.ros.org/question/80936 for details

Interestingly collision_detection_fcl already uses the correct
variable ${LIBFCL_LIBRARIES} although it wasn't even set before. :-)
resolve full path of fcl library

Because it seems to be common practice to ignore ${catkin_LIBRARY_DIRS}
it's more easy to resolve the full library path here instead.
Merge pull request #140 from v4hn/fix-libfcl-include

Fix fcl dependency in CMakeLists.txt