Added Python PLY requirements for the temporal algebra in tgis

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@62113 15284696-431f-4ddb-bdfa-cd5b030d7da7

REQUIREMENTS.html

@@ -149,6 +149,10 @@ Ctypes can be added as a third-party module in Python 2.3 and 2.4
 <a href="http://labix.org/python-dateutil">http://labix.org/python-dateutil</a>
 </li>
 
+<li><b>Python PLY Library</b> ("python-ply", needed for the temporal algebra in tgis)<br>
+<a href="http://www.dabeaz.com/ply">http://www.dabeaz.com/ply</a>
+</li>
+
 <li><b>Python Imaging Library or PILLOW</b> (highly recommended for wxGUI and necessary for wxGUI Cartographic Composer)<br>
 <a href="http://www.pythonware.com/products/pil">http://www.pythonware.com/products/pil</a>,
 a newer version is "python-pillow"