HOW-TO: build OpenCV 2.0 on Ubuntu 64 bits 12.04 LT

Hi all,
Sometimes, you want to build an old version of OpenCV on Ubuntu 64 bits. It seems not to be easy as I think. I met this error. That was suck.

../include/opencv/cxoperations.hpp:1916:15: error: ‘ptrdiff_t’ does not name a type

../include/opencv/cxoperations.hpp:2465:31: error: ‘ptrdiff_t’ does not name a type

The reason is that library might lack of a header file [1]. Just add "#include <cstddef>" to corresponding headers file that generates errors including cxoperations.hpp. And hope it will solve your problem.