wxGUI/vdigit: swig >= 1.3.31 required (sync'ed with devbr6)

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@31349 15284696-431f-4ddb-bdfa-cd5b030d7da7

gui/wxpython/README

@@ -8,6 +8,7 @@ $Date$
  GRASS GIS >= 6.3
  Python >= 2.4
  wxPython >= 2.8.1.1
+ swig >= 1.3.31 (required only for vector digitizer)
  
  Get wxPython 2.8.x packages from:
  * Source: http://www.wxpython.org/download.php