+ make use of GDALOpenShared instead of GDALOpen, which could be better performing when using multiple equal datasource reads (no need to open multiple datasources, and yes it is still thread safe)
+ make use of GDALOpenShared instead of GDALOpen, which could be better performing when using multiple equal datasource reads (no need to open multiple datasources, and yes it is still thread safe)


git-svn-id: 06a2cde72a096d93ff72b88e3e6711b8f00772a4@1131 d397654b-2ff0-0310-9e29-ba003691a0f9

semprebon/mapnik,semprebon/mapnik,semprebon/mapnik,semprebon/mapnik,semprebon/mapnik