check_cpu - new option '--per-cpu'

This option enable the check of CPU utilization for each CPU.
A warning message is returned if at least one CPU exceeds the
warning threshold and no CPU exceed the critical state.
A critical message is returned if at least one CPU exceeds the
critical threshold.

Signed-off-by: Davide Madrisan <davide.madrisan@gmail.com>
check_cpu - print the cpu frequency before the values of each cpu utilization

Signed-off-by: Davide Madrisan <davide.madrisan@gmail.com>