Added checks for "--as-needed" and "--version-script" linker flags.

This makes possible to build Corosync from sources on SunOS 5.11,
Mac OS X 10.8.3 and probably other systems with non-GNU linker.

Signed-off-by: Andrei Belov <defanator@gmail.com>
Reviewed-by: Fabio M. Di Nitto <fdinitto@redhat.com>