Pimpl-ization

[Kohei Yoshida]

It has come to my attention that some folks are feeling a bit uneasy
about my recent pimplization of some of what I call "high impact" public
classes.  I just wanted to make it clear that the reason I'm doing this
is in direct reponse to the discussion we recently had during our ESC
call wrt the bloated object sizes of our shared objects, most notably
those generated from sc and sw modules.

There are 2 main reasons I'm doing this.

1) To reduce the size of our shared objects.
2) To improve our build time.

1) is apparently important for Michael Stahl, and I personally care
about 2) since it directly affects my development efficiency.

My belief was that this was not a controvercial change, but it appears
that it is.  If there is a strong objection I'll stop doing it.  If not,
I'd like to continue pursing this since it seems to improve both of the
2 aforementioned points, and I've only covered perhaps 10-20% of all
possible candidates.

Please share your opinions.

Kohei