function probes don't work in hierarchical blocks

Functions probes don't work in hierarchical blocks. 

A function probe generates a thread body such as:

-------

        def _cross_freq_estimate_probe():

          self.flowgraph_started.wait()

          while True:

            val = self.cross_freq_probe.level()

-------

However, hierarchical blocks don't have a member flowgraph_started.  I don't have a simple suggestion, but perhaps we can pass this member from the parent?  A bit ugly!  Makes the hier blocks dependent on the rest of the GRC framework — i.e. can't easily reuse in python-only design flow.

Eugene Grayver, Ph.D.

Principal Engineer

310-336-1274