RTTI updates

[Jim Dehnert]

I've updated the abi-layout.html page to reflect this morning's decisions
about RTTI issues A-22 and A-23.  Removing the reference type RTTI is
straightforward, but the class type restructuring is a bit different than
what I expected going in (could just be my confusion).

I moved the flags from __class_type_info to __vmi_class_type_info,
discovering that they don't need to share space with the offset field
in the __base_class_info records, but rather with the base class count.
This is actually simpler, but check how I specified that and comment if
you have better ideas.

But, the __base_class_info has its own flags (virtual and public)
which can reasonably share a doubleword, as we were discussing for the
other flags this morning.  So I specified that -- see what you think.
Note that I put the flags in the low byte rather than the high byte.
That is because the offset is signed, and it is likely that
implementations will sign-extend (signed doubleword>>8), but not
(doubleword & 0x00ffffffffffffffll).  If you have other ideas, please
suggest them.

The HTML is updated, not the PDF yet.

Jim

-		Jim Dehnert  x3-4272