o Not all derived methods were marked 'override', but it is a great
feature of C++11 that we should make use of.
o While at it: touched header files got a -*- c++ -*- for emacs to
provide support for that language.
o use YS_OVERRIDE for all override keywords (though we should probably
use the plain keyword going forward now that C++11 is established)
In some cases (e.g. the low bits of counters) the design might end up
with a flip-flop whose input is directly driven by another flip-flop.
This isn't possible in the Coolrunner-II architecture, so add a single
AND term and XOR in this case.
Henner Zeller
Robert Ou
Clifford Wolf