fixed pdflatex compile error

doc/cv_motion_tracking.tex

@@ -726,7 +726,7 @@ Changes the contour position to minimize its energy.
 void cvSnakeImage( \par const IplImage* image,\par CvPoint* points,\par int length,\par float* alpha,\par float* beta,\par float* gamma,\par int coeff\_usage,\par CvSize win,\par CvTermCriteria criteria,\par int calc\_gradient=1 );
 }
 
-\cvdefPy{SnakeImage(image,points,alpha,beta,gamma,win,criteria,calc\_gradient=1)-> new_points}
+\cvdefPy{SnakeImage(image,points,alpha,beta,gamma,win,criteria,calc\_gradient=1)-> new\_points}
 
 \begin{description}
 \cvarg{image}{The source image or external energy field}