Conditionally include <linux/limits.h> and <sys/params.h> on Linux, BSD

<linux/limits.h> should be included conditionally for Linux only, also
SPECNAMELEN used conditionally when the OS is FreeBSD requires to
include <sys/params.h>.

Signed-off-by: Eleni Maria Stea <elene.mst@gmail.com>
Reviewed-by: Eric Engestrom <eric@engestrom.ch>