RFD: support of per script nice(1) value in periodic.conf(5)

[Artem Naluzhnyy]

bin/129814


The patch adds support of per periodic(8) script nice(1) value the
script will be run at (similar to "<service>_nice" variables in
rc.conf). There are two features:

  * default_nice variable - default nice level
  * <basename>_<script>_nice variables - nice level for a specific script

Default behavior after the patch application is still the same - no
nice level changes.

periodic.conf(5) example:

  default_nice=10
  daily_status_mail_rejects_enable="YES"
  daily_status_mail_rejects_nice=8

-- 
Artem Naluzhnyy