RFA: Add builtin bitcounting bitops for xstormy16

[Nick Clifton]

Hi Richard,

>>+   /* Defined in libgcc2.c, exported in _popcountsi2.o.  */
>>+   extern const unsigned char __popcount_tab[];
> 
> I'd prefer if you included "libgcc2.h".  I know this isn't
> currently defined in that header file, but you can fix that.
> I'd be ok with redefining this in terms of UQItype to avoid
> having to frob "bogus" types.

Well how about moving this code into libgcc2.c ?  After all there must 
be other 16-bit ports that would want these functions...

They could be controlled by the presence of #defined symbols such as 
L_clzhi2 and L_ctzhi2 which would be set by mklibgcc.in if a new target 
makefile fragment variable "LIBGGC2_16BIT_BIT_FUNCS" was defined.  (Just 
a suggestion for the name :-)

Cheers
   Nick