CxxUtils: Update checker_macros.h.
Add ATLAS_CTORDTOR_NOT_THREAD_SAFE.
At this point, we also change the gnu:: prefix on the attributes in checker_macros.h to ATLAS::. (Prior to gcc version 7, one could not use a prefix other than gnu::.)
Add ATLAS_CTORDTOR_NOT_THREAD_SAFE.
At this point, we also change the gnu:: prefix on the attributes in checker_macros.h to ATLAS::. (Prior to gcc version 7, one could not use a prefix other than gnu::.)