[v3] weak instantiations for AIX

[David Edelsohn]

	Thanks.  I'm just running a bootstrap now and I updated the
libstdc++ testsuite in the middle of the bootstrap before it got to those
tests, so we'll see how it goes.

	Now we can focus on the real execution failures.  Some of the
failures are locale problems.  For the rest, debugging is difficult
because of GDB and XCOFF stabs limitations.  If there is information I
manually can print from the testcases that can help us track down the
problem, let me know.

Thanks, David