Add internal bitcount functions

[Jeff Law]

On 11/07/2015 05:32 AM, Richard Sandiford wrote:
> This patch adds internal function equivalents of all the INT_FN functions.
> Unlike the math functions, these functions never set errno and the internal
> functions should be exactly equivalent to the built-in ones.  The reason
> for defining the internal functions is so that we can extend the
> functionality to other modes, in particular vector modes.
>
> Tested on x86_64-linux-gnu, aarch64-linux-gnu and arm-linux-gnueabi.
> OK to install?
>
> Thanks,
> Richard
>
>
> gcc/
> 	* internal-fn.def (DEF_INTERNAL_INT_FN): New macro.
> 	(CLRSB, CLZ, CTZ, FFS, PARITY, POPCOUNT): New functions.
> 	* builtins.c (associated_internal_fn): Handle them.
OK.
jeff