Add basic code for primitive shape distance by extending the libccd a bit....

Add basic code for primitive shape distance by extending the libccd a bit. Correctness is tested on basic benchmarks. The external interface will be provided soon.

One small problem is that the precision seems not very high in some cases (like the error is 0.1 when distance is 30). 




git-svn-id: https://kforge.ros.org/fcl/fcl_ros@101 253336fb-580f-4252-a368-f3cef5a2a82b