FindCUDA: Remove duplicate entries from INCLUDE_DIRECTORIES.

As of CMake 2.8.8, the INCLUDE_DIRECTORIES() command does
not de-duplicate entries. Failure to do so can lead to an extremely
long and repetitive list of -I entries on the command line.
Merge topic 'Cuda_WRAP_SRCS_duplicates' into next

32b582d FindCUDA: Remove duplicate entries from INCLUDE_DIRECTORIES.