SQLite: add the capability to use a custom memory allocator for SQLite. Must be enabled at compile time with USE_SQLITE_DEBUG_MEMALLOC and at run-time as well

git-svn-id: https://svn.osgeo.org/gdal/trunk@28048 f0d54148-0727-0410-94bb-9a71ac55c965
GDALDriver::CreateCopy(): accept _INTERNAL_DATASET=YES as creation option, so as to avoid the returned dataset to be registered in the global list of open datasets

git-svn-id: https://svn.osgeo.org/gdal/trunk@28049 f0d54148-0727-0410-94bb-9a71ac55c965
Merge branch 'trunk' into trunk_vc12