Wrap rtpostgis_upgrade.sql in a transaction (#2749)

git-svn-id: http://svn.osgeo.org/postgis/branches/2.1@12592 b70326c6-7e19-0410-871a-916f4a2858ee
Update NEWS with raster upgrade being now done in a transaction

git-svn-id: http://svn.osgeo.org/postgis/branches/2.1@12593 b70326c6-7e19-0410-871a-916f4a2858ee