MEDIUM: config: check the bind-process settings according to nbproc

MEDIUM: config: check the bind-process settings according to nbproc

When a bind-process setting is present in a frontend or backend, we
now verify that the specified process range at least shares one common
process with those defined globally by nbproc. Then if the value is
set, it is reduced to the one enforced by nbproc.

A warning is emitted if process count does not match, and the fix is
done the following way :
  - if a single process was specified in the range, it's remapped to
    process #1
  - if more than one process was specified, the binding is removed
    and all processes are usable.

Note that since backends may inherit their settings from frontends,
depending on the declaration order, they may or may not be reported
as warnings.