random: Use getentropy when available for not GNU/Linux.
* configure.ac: Detect getentropy. * random/rndlinux.c [__linux__] (getentropy): Macro defined. [HAVE_GETENTROPY] (_gcry_rndlinux_gather_random): Use getentropy.
- GnuPG-bug-id: T4288
- Reported-by: David Carlier
- Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>