Atomic ops in PAPI

[Anthony Danalis]

Earlier this year we committed a change to how PAPI handles atomic
operations in the branch "libatomic_ops"
(https://bitbucket.org/icl/papi/src/libatomic_ops/)
to allow 3rd party testing before merging into the master. If you have
any feedback you would like to share, or if you want to have a
discussion about it, please do so soon so that we can proceed with the
merge.

thanks,
Anthony