[CAN] Style, doxygen and name groups fixes. Possible BUG found and documented.
[CAN] Allow index-addressing of mailboxes
[CAN] Add more index-like accesses to the registers
[CAN] Use the index-like registers
[CAN] Added functions for bit timing computation, added low-level accessors for mode selection.
[DOXYGEN:CAN] Add documentation blocks to the new functions
[CAN:IRQ] Add irq manipulation