GPKG: remove dead code and test differed spatial index dropping

git-svn-id: https://svn.osgeo.org/gdal/trunk@27358 f0d54148-0727-0410-94bb-9a71ac55c965
Fix compilation with mingw-w64 cross-compiler in -std=c++11 mode (#5459)

git-svn-id: https://svn.osgeo.org/gdal/trunk@27359 f0d54148-0727-0410-94bb-9a71ac55c965
Fix MSSQL spatial geometry field handling (#5474)

git-svn-id: https://svn.osgeo.org/gdal/trunk@27360 f0d54148-0727-0410-94bb-9a71ac55c965
Refactor OGRSQLiteSelectLayer so that GPKG can share code with it

git-svn-id: https://svn.osgeo.org/gdal/trunk@27362 f0d54148-0727-0410-94bb-9a71ac55c965
Merge branch 'trunk' of git://github.com/OSGeo/gdal into unification