Add a check for -Wl, --wrap support in linker

Add a check for -Wl, --wrap support in linker

- Also make tests that require --wrap option to be
  conditional on this support

[ DS: Removed AC_DEFINE([HAVE_LD_WRAP_SUPPORT],...) at commit time
      as we now see no real use for such a #define in config.h ]

Signed-off-by: Selva Nair <selva.nair@gmail.com>
Acked-by: Gert Doering <gert@greenie.muc.de>
Acked-by: David Sommerseth <davids@openvpn.net>
Message-Id: <1484772172-19758-1-git-send-email-selva.nair@gmail.com>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg13897.html
Signed-off-by: David Sommerseth <davids@openvpn.net>