Do not ask for target platform relax when useless

When the platform contains unadapted packages, installed with the relax option, it is useless to ask again for a relax when any request would require it.

Detect if the platform is in a "relaxed" state and replace the user confirmation by a warning.

Ideally, check if the request involves new relaxes... and/or if the unadapted packages can be ignored to satisfy the current request.