opencv: Adds patch for opencv bug: http://code.opencv.org/issues/3191

Hey,

I had problems installing opencv on OS X 10.9 and found issue #402 which was pretty much what I was experiencing. None of the mentioned cures brought any remedy so I looked a bit around opencv and it looks like this is a known bug on their end: http://code.opencv.org/issues/3191

This pull requests applies this [patch](http://code.opencv.org/projects/opencv/repository/revisions/e9b9a6fc038fc243e2debcc1dabd0d0745ff39d6/diff/modules/legacy/src/dpstereo.cpp) from opencv 2.4.7 to the formula which made me able to install that beast just fine.