sar: Display values in human readable format

sar: Display values in human readable format

Take into account new "--human" option to display values in human
readable format.
Functions cprintf_f() cprintf_u64() are modified to add the unit after
the value if requested.
Only a few options are concerned for sar.
Other commands are updated too, but the option will be activated in
separate patches.

Signed-off-by: Sebastien GODARD <sysstat@users.noreply.github.com>