FileGDB: implement ref counting of the FileGDB SDK API' Geodatabase* object to avoid issues on Linux 64bit with interleaved opening and closing of databases (#4270)

git-svn-id: https://svn.osgeo.org/gdal/trunk@26307 f0d54148-0727-0410-94bb-9a71ac55c965
Merge branch 'trunk' into trunk_travis_macosx