Let \partial in mid-piece work via a finalization hook

Let \partial in mid-piece work via a finalization hook

That allows all other processing to complete before measurePosition is
adjusted.  In particular, this avoids problems when multiple parallel
contexts invoke \partial and/or bar checks.


Also contains commit:
Regtest for \partial in mid-piece

[dak, 2014-08-08 20:57:24]

Wait for finalization before getting Timing values