[PATCH] Fix make check build warnings in libm

[Siddhesh Poyarekar]

On Fri, Feb 15, 2013 at 09:44:34PM -0500, Carlos O'Donell wrote:
> 
> What about this commented out line?
> 
> Why are we using chk if all the assert's on chk are commented out?
> 
> >           chk |= (n ? mpn_sub_n : mpn_add_n)(d,ss,tmp,SZ);                    \
> >          /* assert(chk == 0); */                                              \
> 

I'm not sure why, but most mpn functions seem to return carry or
borrow if any or just zero.  It's been that way since inclusion
(1997), so it might make sense to just remove them.  I don't think any
of the inputs will cause an overflow and the checks were probably
there earlier for debugging.

Siddhesh