ogrFeatureToSlot(): use GIntBig to store value got by OGR_F_GetFID() for GDAL 2.0 Win64 portability
ogrFeatureToSlot(): use GIntBig to store value got by OGR_F_GetFID() for GDAL 2.0 Win64 portability

pramsey/pgsql-ogr-fdw,mysidewalk/pgsql-ogr-fdw,pramsey/pgsql-ogr-fdw