Return a status from buddy_safe_free

[spaskalev]

The intention for buddy_safe_free is to avoid freeing a slot just because it matches in location but doesn't match in size. A call like this is unconditionally a bug in the calling code and calling code should be made aware of it so that it can assert and fail early (as opposed to currently the free doing nothing and leaking memory, therefore delaying the failure until the arena is eventually unable to satisfy a request)

[spaskalev]

A meaningful status is now returned from buddy_safe_free that can be used to assert and fail quickly.