fix handling of method field mapping to output fields when output fields are precreated (#5089)

git-svn-id: https://svn.osgeo.org/gdal/branches/1.10@26015 f0d54148-0727-0410-94bb-9a71ac55c965
Fix crash in CleanupESRIDatumMappingTable() if it is called twice (#5090, patch by freekvw)

git-svn-id: https://svn.osgeo.org/gdal/branches/1.10@26018 f0d54148-0727-0410-94bb-9a71ac55c965