Re: rs6000.c forward declaration cleanup

> This removes rather a lot of forward declarations in rs6000.c, most of
> which existed to satisfy an early TARGET_INITIALIZER.  Now that the
> TARGET_INITIALIZER has been moved to the end of rs6000.c, they become
> unnecessary and wrongly give the impression that rs6000.c style is to
> declare functions at the beginning of the file.  Bootstrapped etc.
> powerpc-linux.  OK to apply?
>
>        * config/rs6000/rs6000.c: Delete unnecessary forward declarations.
>        Move those with ATTRIBUTE_UNUSED to immediately before definitions.
>        Move function pointer variables after forward declarations.
>        (rs6000_builtin_support_vector_misalignment): Make static.
>        (rs6000_legitimate_address_p, rs6000_gimplify_va_arg): Likewise.
>        (rs6000_function_value, rs6000_can_eliminate): Likewise.