v.buffer manual: demystify caps

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@68013 15284696-431f-4ddb-bdfa-cd5b030d7da7

vector/v.buffer/v.buffer.html

@@ -38,7 +38,7 @@ buggy for some input data).
 
 <h3>Corner settings</h3>
 
-The following corners (also called "cap") exist:
+The following vector line related corners (also called "cap") exist:
 <ul>
 <li>no cap: &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <img src="v_buffer_no_cap.png" valign="middle" alt="line buffer: no cap"></li>
 <li>rounded cap: <img src="v_buffer_rounded_cap.png" valign="middle" alt="line buffer: rounded cap"></li>