src: add syscall_overhead

A program to measure the system call overhead

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
src: syscall_overhead use "common" shared functions

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Merge branch 'master' of github.com:netoptimizer/network-testing

Forgot to pull, before pushing from my laptop