Keyboard queue/stack behavior is undefined

[azertyfun]

As-is, the official spec for the keyboard only says Store next key from buffer to C register, or 0 if the buffer is empty, but does not state wether keys are stored in a queue or a stack (FIFO vs LIFO), and does not state the length of the queue (though I guess that should be undefined because it is dependent on the model?).

@l3nn0x mentionned that notch's emulator used to be 16 keys FIFO, so there's that bit of info I guess.

[andyleap]

Current hardware is 8 item FIFO queue, updated the spec to match.

[Yamakaky]

LIFO would be strange ^^