MEDIUM: cfgparse: detect numa and set affinity if needed

MEDIUM: cfgparse: detect numa and set affinity if needed

On process startup, the CPU topology of the machine is inspected. If a
multi-socket CPU machine is detected, automatically define the process
affinity on the first node with active cpus. This is done to prevent an
impact on the overall performance of the process in case the topology of
the machine is unknown to the user.

This step is not executed in the following condition :
- a non-null nbthread statement is present
- a restrictive 'cpu-map' statement is present
- the process affinity is already restricted, for example via a taskset
  call

For the record, benchmarks were executed on a machine with 2 CPUs
Intel(R) Xeon(R) CPU E5-2680 v3 @ 2.50GHz. In both clear and ssl
scenario, the performance were sub-optimal without the automatic
rebinding on a single node.