* aix5ppc-core.c: Define macros for the default architecture and

   * aix5ppc-core.c: Define macros for the default architecture and
       machine for matching core files.
       (xcoff64_core_p): Set the architecture and machine to the default
       values defined in the macros mentioned above.
       * rs6000-core.c: Define macros to determine whether or not the
       core file header uses the core_dumpxx header format.
       (rs6000coff_core_p): Don't match core files that use the
       core_dumpxx header format.