lib/malloca.c, different signs of integers; with clang and groff

[Bjarni Ingi Gislason]

  CC       lib/libgnu_a-malloca.o
../lib/malloca.c:61:38: warning: comparison of integers of
different signs: 'size_t' (aka 'unsigned long') and 'idx_t' (aka
'long') [-Wsign-compare]
  if (!ckd_add (&nplus, n, plus) && !xalloc_oversized (nplus, 1))
                                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~
../lib/xalloc-oversized.h:62:33: note: expanded from macro
'xalloc_oversized'
# define xalloc_oversized(n, s) __xalloc_oversized (n, s)
                                ^~~~~~~~~~~~~~~~~~~~~~~~~
../lib/xalloc-oversized.h:33:8: note: expanded from macro
'__xalloc_oversized'
       < (n)))
       ^  ~
1 warning generated.