[PATCH 21.5] Union type fixes

[Jerry James]

I wrote:
> This fixes a problem I have encountered when using GCC 4.1.  I never had
> trouble with earlier versions of GCC, nor with icc.  With newer GCCs,
> apparently references to bit-restricted fields keep the bit restriction
> in subsequent arithmetic operations.  This breaks a lot of the bignum
> code, in particular.

I just wanted to let other developers know that bignums are broken with
GCC 4.X + optimization, period.  The patch mentioned above does fix
things up a little, but what appears to be a GCC code generation bug
breaks bignums badly if any optimization whatsoever is turned on.  See
gcc bug 28045 for more information.

I would still like to commit the patch mentioned above, if there are no
objections, since my reading of the C99 spec indicates that it is
necessary.  On the other hand, I am not a language lawyer.
-- 
Jerry James, Assistant Professor        james at xemacs.org
Computer Science Department             http://www.cs.usu.edu/~jerry/
Utah State University