When compiling the zbxcomms library on AIX, we noticed that hstrerror() was being detected during configure's feature tests, but the compiler raises a warning when compiling the comms.c module, as it fails to see the prototype for the function, which is behind a feature guard macro (_USE_IRS) on AIX, which we don't define.

Linux marks gethostby*(3) and hstrerror(3) to be obsolete, and advises switching to getaddr*(3) and gai_strerror(3) instead.

We already use the getaddr*(3) family and the use of hstrerror(3) seems to be an artefact, so I suggest we just make the leap and switch.