Added rollback emulation to spatialite backend; refs #22487.
Simplified handling of use_debug_cursor.

Turned it from a tri-valued boolean into a regular boolean.
Fixed #20420 -- Normalized query counts on Oracle.

This is achieved by inserting a fake entry in connection.queries when
not releasing a savepoint (since Oracle doesn't support that operation.)

Also removed the can_release_savepoints feature that was recently added,
but is superseded by this solution.
Dropped support for SpatiaLite < 2.4.
Removed unused import.
Fixed #17552 -- Removed a hack for IE6 and earlier.

It prevented the GZipMiddleware from compressing some data types even on
more recent version of IE where the corresponding bug was fixed.

Thanks Aaron Cannon for the report and Tim Graham for the review.
Fixed #14334 -- Query comparision now check for object types.