Improved atomics API.

Made the atomic API compatible with std::atomic such that we
can easily substitute std::atomic when available. This API
also requires no change by the users of ReferenceCount.

Change-Id: I078c29d92fcee5fd444c0eb675bceca695c89667
Merge topic 'improved-atomic-api' into master

92f6db75 Improved atomics API.
Fixed minor issue in CMake code.

Should have used list(APPEND ...) instead of set().

Change-Id: I858e662f4086eda1a3494bfc921c431d11959157
Fixed wrong WRAP_EXCLUDE use.

WRAP_EXCLUSE expects .cxx files instead of .h when one exists.
Fixed.

Change-Id: I393f764cb324b991d423b7497f64263cc909125c
Merge topic 'fixed-wrap-ignore' into master

1cac14df Fixed wrong WRAP_EXCLUDE use.
6a7b1efa Fixed minor issue in CMake code.