Re-use dead Compiler.Waveform label code for better pretty printing.
Re-use dead Compiler.Waveform label code for better pretty printing.

We previously used the Waveform label property to mark a location in a sequence.
But, we now have the discrete BlockLabel object. So, we can now use this
property to carry the original label of the Pulse.

BBN-Q/QGL,BBN-Q/QGL