add environment variables POSTGIS_ENABLE_OUTDB_RASTERS and POSTGIS_GDAL_ENABLED_DRIVERS

git-svn-id: http://svn.osgeo.org/postgis/branches/2.0@12497 b70326c6-7e19-0410-871a-916f4a2858ee
remove #define directive

git-svn-id: http://svn.osgeo.org/postgis/branches/2.0@12498 b70326c6-7e19-0410-871a-916f4a2858ee