CanFestival CAN interfaces

Because most CAN controllers and drivers implement FIFOs, CanFestival consider sending message as a non bloking operation.

In order to prevent reentrent calls to the stack, messages reception is implemented differently on µC and OS.:

1. µC must provide interuption masking for timer and can receive IT
   
   
2. OS must provide a receive thread, a timer thread and a mutex. CAN reception is a bloking operation.