MFC 330711:
Permit sysctl(8) to set an array of numeric values for a single node.

Most sysctl nodes only return a single value, but some nodes return an
array of values (e.g. kern.cp_time). sysctl(8) understand how to display
the values of a node that returns multiple values (it prints out each
numeric value separated by spaces). However, until now sysctl(8) has
only been able to set sysctl nodes to a single value. This change
allows sysctl to accept a new value for a numeric sysctl node that contains
multiple values separated by either spaces or commas. sysctl(8) parses
this list into an array of values and passes the array as the "new" value
to sysctl(2).

Sponsored by: Chelsio Communications