* config/rs6000/xm-darwin.h: New file, Darwin host definitions.
        * config/rs6000/x-darwin: New file, Darwin host fragment.
        * config.gcc (powerpc-*-darwin*): New host.
        * system.h (HAVE_DESIGNATED_INITIALIZERS):  Allow this to be
        overridden by a config file.

From-SVN: r37601