Fixed django#17672 -- Precised MacPorts GeoDjango install instruction…

…s to install gdal with geos support. Thanks chosak for the report and the patch.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@17883 bcc190cf-cafb-0310-a4f2-bffc1f526a37

docs/ref/contrib/gis/install.txt

@@ -938,7 +938,7 @@ Summary::
     $ sudo port install geos
     $ sudo port install proj
     $ sudo port install postgis
-    $ sudo port install gdal
+    $ sudo port install gdal +geos
     $ sudo port install libgeoip
 
 .. note::