v.buffer manual: example updated to NC; screenshot added

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@58686 15284696-431f-4ddb-bdfa-cd5b030d7da7

vector/v.buffer/v.buffer.html

@@ -34,6 +34,12 @@ All examples are based on the North Carolina sample dataset.
 v.buffer input=roadsmajor output=roadsmajor_buffer type=line distance=100
 </pre></div>
 
+<center>
+<img src="v_buffer_lines.png" border="1"><br>
+Buffer of 100m along the "roadsmajor" lines (map subset, original center line
+shown in black)
+</center>
+
 <h3>Circles around input points</h3>
 
 <div class="code"><pre>