automatic --disable-multilib

[Jack Howarth]

   Shouldn't configure in gcc be made to
automatically test if -m64 is working on
the build machine in question and automatically
invoke --disable-multilib if not? Currently
on Darwin for example we have to explicitly
invoke --disable-multilib when building on
G4's or non-EMT64 Macintel machines. It would
much better if configure would automatically
handle this.
                   Jack