[1.4.X] Fixed #17672 -- Precised MacPorts GeoDjango install instructions to...

[1.4.X] Fixed #17672 -- Precised MacPorts GeoDjango install instructions to install gdal with geos support. Thanks chosak for the report and the patch.

Backport of r17883 from trunk.


git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.4.X@17884 bcc190cf-cafb-0310-a4f2-bffc1f526a37