Changeset 9761:a04648a0d2c6
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sim: Pre-compute the clock period

This patch changes the source and derived clock domain such that no
virtual functions or multiplications are needed when calling
clockPeriod. Instead, the clock period is pre-computed when any
changes occur. For this to be possible, a clock domain must be aware
of its children and the corresponding data structures and methods have
been added to facilitate this.

All regressions pass