mc6845: converted to devcb2, delegates and inline configs. nw.

while at it, cleaned up the args of the mc6845 delegates as well 
(no need to pass back and forth pieces of the driver class, now 
that delegates belong to it as well)

even if I tested the changes extensively, I might have missed 
something among the 177 source files using this, so please report
any regressions you see :)