subclasses of x++

[Roger Gregory <roger>]

I find that I want a subclass of BitArray.  I want to add some character interpretation
stuff to it, like isSeparator & isLineBreak.  Will these cause a problem with the LEAF
declarations in the CLASS definition.  I certainly will have a problem if I want to
override any of the leaf methods.  I assume we haven't thought about this much, but
it should be little problem to make things virtual if we do it in a careful way.
The problem I see is efficiency, on this low-level stuff we will probably have to make the
code inline anyway, and I expect that virtual will cause us some problems there (at best some
execution speed).