[PATCH/RFA] rs6000: TARGET_CPU_CPP_BUILTINS tweak

[David Edelsohn]

        * config/rs6000/rs6000.h (RS6000_CPU_CPP_ENDIAN_BUILTINS): New.
        * config/rs6000/rs6000-c.c (rs6000_cpu_cpp_builtins): Use
        RS6000_CPU_CPP_ENDIAN_BUILTINS.
        * config/rs6000/netbsd.h (RS6000_CPU_CPP_ENDIAN_BUILTINS): Redefine.

This patch is okay, but I am concerned about the maintainability of adding
too many target-specific tweaks like this.

David