Better glibc compatibility for getline/getdelim:

Better glibc compatibility for getline/getdelim:

- Tolerate applications that pass a NULL pointer for the buffer and
  claim that the capacity of the buffer is nonzero.

- If an application passes in a non-NULL buffer pointer and claims the
  buffer has zero capacity, we should free (well, realloc) it
  anyway. It could have been obtained from malloc(0), so failing to
  free it would be a small memory leak.

MFC After:	2 weeks
Reported by:	naddy
PR:		ports/138320