64-bit configure hell

[Benjamin Kosnik]

I think if you search through libstdc++ bugzilla you will find reports
of oddness with x86_64 systems and the 64 bit multilib. To me, if you
have to disable multilibs on 32/64 bit systems to get a working
toolchain, something is wrong.

I haven't paid much attention to these bug reports. Some people have
problems (HJ) and others do not (Jakub, Paolo, others). 

If you can provide a real problem description, and examples of the
libstdc++ build/configure hacks you use to work around it, it would be
helpful.

-benjamin