[Bf-codereview] Distance Node YCC implementation (issue 6462050)

[dfelinto at gmail.com]

Reviewers: bf-codereview_blender.org, jbkkavt,

Description:
The Distance Node in 2.49 has a different calculation for RGB and YCC.
While RGB calculate the distance in 3d between R,G and B, the YCC only
takes Cb and Cr into consideration.

See if this implementation is ok.
Basically I:
- renamed COM_DistanceMatteOperation into COM_DistanceRGBMatteOperation
- turned the private properties into private
- isolated the distance calculation function into a new function
- inherited this file for the COM_DistanceYCCMatteOperation
- overriding the function calculateDistance.

Thanks,
Dalai

Please review this at http://codereview.appspot.com/6462050/

Affected files:
   source/blender/compositor/CMakeLists.txt
   source/blender/compositor/nodes/COM_DistanceMatteNode.cpp
   source/blender/compositor/operations/COM_DistanceMatteOperation.cpp
   source/blender/compositor/operations/COM_DistanceMatteOperation.h
   source/blender/compositor/operations/COM_DistanceRGBMatteOperation.cpp
   source/blender/compositor/operations/COM_DistanceRGBMatteOperation.h
   source/blender/compositor/operations/COM_DistanceYCCMatteOperation.cpp
   source/blender/compositor/operations/COM_DistanceYCCMatteOperation.h