tst-fanotify: check for linux/fanotify.h existence

We support older kernels that lack this header, so check for it
before we try to use it.

Reported-by: Adhemerval Zanella <azanella@linux.vnet.ibm.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
NEWS: mention 16379 as fixed

Reported-by: Joseph S. Myers <joseph@codesourcery.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>