Allow for more options to be grouped together.

Sysstat command options can now be 'collapsed' (grouped) when
not followed by an argument. So it's now possible for example
to enter 'iostat -px 2 5' since no device name is given to
option -p.
This also concerns pidstat option -U: You can now enter for example
'pidstat -wU' to display switching activity for tasks together with
their user name.