Limits the number of clock buffer fanouts to the number
you specify.
If you specify the MaxFanout statement and the
setCTSMode -useLibMaxFanout true parameter,
CTS uses the worst case constraint specified.
CTS does not support a fanout_load that is not equal
to 1.
Note: CTS considers the MaxFanout statement to be a
soft constraint. CTS will try to meet it, but might need to
make adjustments in order to meet physical constraints.