convert-ly dummy rules

[Graham Percival]

Could I propose that we use the following convert-ly rule
for all version numbers[1]?  It will make users feel better if their
files are "up to date", even if nothing has changed, and I don't
think that having such a conversion rule would hurt anything.


[1]  ie replace "(2, 4, 0)" with "to_version" in the excerpt below.

------
# nothing, just to make version numbers look good.
def conv (str):
        return str

conversions.append (((2, 4, 0),
                     conv,
                     ''))
------

Cheers,
- Graham