basic support for GDAL 2.0

git-svn-id: http://svn.osgeo.org/postgis/branches/2.1@12582 b70326c6-7e19-0410-871a-916f4a2858ee
news entry for GDAL 2.0

git-svn-id: http://svn.osgeo.org/postgis/branches/2.1@12583 b70326c6-7e19-0410-871a-916f4a2858ee