[FIX] MAC OSX search path for includes of the niftilib (macports puts them...

[FIX] MAC OSX search path for includes of the niftilib (macports puts them into /opt/local/include/nifty by default)

tools/cmake/Findniftilib.cmake

@@ -6,7 +6,7 @@
 #   * NIFTILIB_LIBRARY - the path to the library
 #
 
-FIND_PATH( NIFTILIB_INCLUDE_DIR nifti1.h /usr/include/nifti /usr/local/include/nifti /opt/local/include )
+FIND_PATH( NIFTILIB_INCLUDE_DIR nifti1.h /usr/include/nifti /usr/local/include/nifti /opt/local/include/nifti )
 
 # This hack is inspired by FindBoost.cmake. It ensures that only shared objects are found. Linking a SO with a static lib is not possible 
 # in Linux. On other systems, this should be no problem.