couple more hyperlinks fixed

doc/opencv_cheatsheet.tex

@@ -521,9 +521,9 @@ samples on what are the contours and how to use them.
 
 \begin{tabbing}
 \textbf{Wr}\=\textbf{iting and reading raster images}\\
-\texttt{imwrite("myimage.jpg", image);}\\
-\texttt{Mat image\_color\_copy = imread("myimage.jpg", 1);}\\
-\texttt{Mat image\_grayscale\_copy = imread("myimage.jpg", 0);}\\
+\texttt{\href{http://opencv.willowgarage.com/documentation/cpp/reading_and_writing_images_and_video.html\#cv-imwrite}{imwrite}{imwrite}("myimage.jpg", image);}\\
+\texttt{Mat image\_color\_copy = \href{http://opencv.willowgarage.com/documentation/cpp/reading_and_writing_images_and_video.html\#cv-imread}{imread}("myimage.jpg", 1);}\\
+\texttt{Mat image\_grayscale\_copy = \href{http://opencv.willowgarage.com/documentation/cpp/reading_and_writing_images_and_video.html\#cv-imread}{imread}("myimage.jpg", 0);}\\
 \end{tabbing}
 
 \emph{The functions can read/write images in the following formats: \textbf{BMP (.bmp), JPEG (.jpg, .jpeg), TIFF (.tif, .tiff), PNG (.png), PBM/PGM/PPM (.p?m), Sun Raster (.sr), JPEG 2000 (.jp2)}. Every format supports 8-bit, 1- or 3-channel images. Some formats (PNG, JPEG 2000) support 16 bits per channel.}