title: Missing face.hpp in OpenCV 3.1.0 after successful build with opencv_contrib modules
body: <p>I am doing a project in C++ using OpenCV and stuck with adding face recognition module </p>
  
  <p>I have built without errors the Extra modules of OpenCV (opencv_contrib) using the following make commands</p>
  
  <pre><code>$ cmake -D CMAKE_BUILD_TYPE=RELEASE OPENCV_EXTRA_MODULES_PATH=../opencv_contrib/modules ../opencv-3.1.0  
  $ make 
  $ sudo make install
  </code></pre>
  
  <p>My code involves the following as I copied the code for testing</p>
  
  <pre><code>#include "opencv2/core/core.hpp"
  #include "opencv2/highgui/highgui.hpp"
  #include "opencv2/imgproc/imgproc.hpp"
  #include "opencv2/objdetect/objdetect.hpp"
  #include "opencv2/face.hpp"        //-----&gt; Doesn't exist
  </code></pre>
  
  <p>This shows the following error when I attempt building the code in code::blocks :</p>
  
  <pre><code>~/Desktop/OpenCV_Project/OpenCv_Demos/Face_Recognition/main.cpp|6|fatal error: opencv2/face.hpp: No such file or directory|
  </code></pre>
  
  <p>I have searched the linked directories too, there is no file as face.hpp</p>
  
  <p>How do I ensure that the extra modules were really built with openCV source after make/make install?</p>
  
  <p>Other requisites:<br>
  Ubuntu 15.10<br>
  Code::blocks 16.10<br>
  gcc version 5.2.1 </p>