* add requirement to use only types T for spin lock, where the behavior Send is specified
* remove obsolete implementation of a irqsave refcell
* replace DoubleLinkedList by LinkedList of the alloc library
* using of the core collection library to handle memory and tasks
* the vector of PCI adapters aren't longer protected by a lock because these adapter are initialized at boot time. Afterwards, we have only read-access.
* Freelist: add check if a reunion with the previous slot is possible