Makefile.in: Move BOOT_CFLAGS above host makefile fragment include.

       * Makefile.in: Move BOOT_CFLAGS above host makefile fragment include.
       * configure.in: add test for powerpc-*-darwin* to specify makefile frag
       * configure: regenerate
       * config/mh-ppc-darwin: create file, override BOOT_CFLAGS for
         -mdynamic-no-pic

From-SVN: r86902