Clarify licensing of PostGIS core as GPL2+ (#2515)

git-svn-id: http://svn.osgeo.org/postgis/branches/2.1@12065 b70326c6-7e19-0410-871a-916f4a2858ee
Reword raster license change NEWS item (#2514)

git-svn-id: http://svn.osgeo.org/postgis/branches/2.1@12068 b70326c6-7e19-0410-871a-916f4a2858ee