Itseez/opencv — pull request #3515 by StevenPuttemans (2014-12-15 10:34:35+00:00)
Title: add extra to FeatureDetector docs

It is quite hard for my students to understand why SIFT and SURF need extra includes and how to get it to work. Seeing the amount of SO topics with this problem, I decided to add a little explanation to make it work for everyone.