fix download links

git-svn-id: http://svn.osgeo.org/postgis/branches/1.5@11005 b70326c6-7e19-0410-871a-916f4a2858ee
fix svn to point to 1.5 branch

git-svn-id: http://svn.osgeo.org/postgis/branches/1.5@11006 b70326c6-7e19-0410-871a-916f4a2858ee