Clarify units used in clock stepping constants.

Signed-off-by: Miroslav Lichvar <mlichvar@redhat.com>
Set printf format attribute for print().

This allows gcc to check format strings used in pr_* calls.

Signed-off-by: Miroslav Lichvar <mlichvar@redhat.com>
Fix new -Wformat warnings.

Signed-off-by: Miroslav Lichvar <mlichvar@redhat.com>