AIX atomicity.h support

[David Edelsohn]

>>>>> Mark Mitchell writes:

Mark> Alexandre, since you are a libtool expert, would you mind working with
Mark> David to see if you can identify and fix the libtool problems?

	Various people inside and outside IBM have been improving libtool
on AIX.  The individual at IBM, Dan McNichol, has been in contact with
Alexandre.  The various individuals are merging their parallel efforts
together for integration into both libtool 1.3.X and libtool 1.4.X.  Those
improvements to libtool will need to be imported into GCC for libstdc++-v3
to build.

David