Can't use old c functions in opencv 3.1

Question

opencv3.1 is build with cmake from latest stable. Trying a cpp example project works fine.

I tried the hello-world example from:

http://www.cs.iit.edu/~agam/cs512/lect-notes/opencv-intro/opencv-intro.html

test.c

////////////////////////////////////////////////////////////////////////
//
// hello-world
//
// This is a simple, introductory OpenCV program. The program reads an
// image from a file, inverts it, and displays the result. 
//
////////////////////////////////////////////////////////////////////////
#include <stdlib.h>
#include <stdio.h>
#include <math.h>
#include <cv.h>
#include <highgui.h>


int main(int argc, char *argv[])
{
  IplImage* img = 0; 
  int height,width,step,channels;
  uchar *data;
  int i,j,k;

  if(argc<2){
    printf("Usage: main <image-file-name>\n\7");
    exit(0);
  }

  // load an image  
  img=cvLoadImage(argv[1]);
  if(!img){
    printf("Could not load image file: %s\n",argv[1]);
    exit(0);
  }

  // get the image data
  height    = img->height;
  width     = img->width;
  step      = img->widthStep;
  channels  = img->nChannels;
  data      = (uchar *)img->imageData;
  printf("Processing a %dx%d image with %d channels\n",height,width,channels); 

  // create a window
  cvNamedWindow("mainWin", CV_WINDOW_AUTOSIZE); 
  cvMoveWindow("mainWin", 100, 100);

  // invert the image
  for(i=0;i<height;i++) for(j=0;j<width;j++) for(k=0;k<channels;k++)
    data[i*step+j*channels+k]=255-data[i*step+j*channels+k];

  // show the image
  cvShowImage("mainWin", img );

  // wait for a key
  cvWaitKey(0);

  // release the image
  cvReleaseImage(&img );
  return 0;
}

When copying the source code to a local *.c file, I get the following errors, while compiling:

gcc `pkg-config --cflags opencv` -Wall -O2 `pkg-config --libs opencv` -lm -o test test.c
/tmp/ccyRzO8F.o: In Funktion `main':
test.c:(.text.startup+0x32): Nicht definierter Verweis auf `cvLoadImage'
test.c:(.text.startup+0x78): Nicht definierter Verweis auf `cvNamedWindow'
test.c:(.text.startup+0x89): Nicht definierter Verweis auf `cvMoveWindow'
test.c:(.text.startup+0xed): Nicht definierter Verweis auf `cvShowImage'
test.c:(.text.startup+0xf9): Nicht definierter Verweis auf `cvWaitKey'
test.c:(.text.startup+0x104): Nicht definierter Verweis auf `cvReleaseImage'
collect2: error: ld returned 1 exit status
make: *** [prog] Fehler 1

How can I get it work?