New -turbo flag and extensive refactoring

During the execution of a (add), it is now possible to use the new -turbo switch,
which enables a different algorithm compared to the standard one.

The expected result is a performance improvement that can reach up to +50% in the most favorable scenarios, and typically ranges between +10% and +20% depending on the use case.

Additionally, this part of the program has undergone extensive refactoring, which is still ongoing.

This may have (and very likely has) introduced new bugs.

Since this is currently a poorly tested area, it can only be enabled explicitly by the user via the -turbo flag.

Pay close attention: do not blindly trust this feature, as it is under active development.

dump command rewritten

The dump command has been almost completely rewritten, removing part of the legacy Mahoney code.
It should now work correctly with archives of any size.