Adding balanced_p parameter to bsg_reduce

[dpetrisko]

This is useful for constructing trees of balanced clock ors/ands

[taylor-bsg]

@dpetrisko the implementation is intended to allow the synthesizer to auto-balance. but why add the parameter, if it is unused?

[dpetrisko]

Used in the hard/ version, otherwise you can get a parameter error when swapping

[taylor-bsg]

Maybe add a comment to that effect