COMP: Update to use latest release OpenCV

Hans: We were using our own patch on OpenCV to build, and I decided to try to use the current release version.  Both the old branch and the current OpenCV 2.4.9 throw a bunch of warnings.

I tried using your branch with some of the fixes for warnings, but rebasing that patch on the current OpenCV  seemed to be tricky.  I can try to re-apply your changes where appropriate.  As it is, this branch is no more 'warning-y' than the previous one used in BRAINSTools.