requirements: note PIL for wxGUI Cartographic Composer

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@52240 15284696-431f-4ddb-bdfa-cd5b030d7da7

REQUIREMENTS.html

@@ -168,10 +168,13 @@ Ctypes can be added as a third-party module in Python 2.3 and 2.4
 gui/wxpython/README)<br>
 <a href="http://www.wxpython.org">http://www.wxpython.org</a>
 
-<li><b>NumPy &gt;= 1.0.4</b> (for wxPython-based GUI tools, see
+<li><b>NumPy &gt;= 1.0.4</b> (for various wxGUI components, see
  file gui/wxpython/README)<br>
 <a href="http://numpy.scipy.org">http://numpy.scipy.org</a>
 
+<li><b>Python Imaging Library</b> (for wxGUI Cartographic Composer (preview mode), see
+ file gui/wxpython/README)<br>
+<a href="http://www.pythonware.com/products/pil">http://www.pythonware.com/products/pil</a>
 
 <li><b>FFMPEG</b> (for direct rendering of animations from NVIZ),
     including libavcodec, libavformat, libswscale <BR>