keys: move key definitions into translation includes

keys: move key definitions into translation includes

Partially reverts the split in commit v1.3-0-g2034c72e12 (2010-06-18)
[overhaul keyboard module include syntax], though keeps distinct keys.
Expected translations did not occur, while normal maintenance becomes much
harder with separated data.  Also translating can easily be done on top of
English includes without significant disadvantages.