mainline AIX bootstrap broken in libstdc++-v3

[David Edelsohn]

>>>>> Benjamin Kosnik writes:

>> Are all allocators compiled even when not used?

Ben> Yes. We do this so that, when a different allocator is desired and
Ben> configured via --enable-libstdcxx-allocator, we don't have to play games
Ben> with any of the instantiation files.

Ben> There are ways around this, by adding complexity, that frankly are not
Ben> worth it.

	I do not have an objection to building all allocators.  I simply
was surprised to see an mt_allocator failure while building on AIX.

David