VRT: add support for multiple geometry fields in OGRVRTWarpedLayer

git-svn-id: https://svn.osgeo.org/gdal/trunk@26987 f0d54148-0727-0410-94bb-9a71ac55c965
VRT: fix direct geometry assignment for first geometry field in SetFeature() / CreateFeature()

git-svn-id: https://svn.osgeo.org/gdal/trunk@26988 f0d54148-0727-0410-94bb-9a71ac55c965