- Add new object BLACKHOLE_BQ: now a BLACKHOLE is defined as having an
  empty blocking queue, and the first time a thread blocks on a BLACKHOLE
  it is changed into a BLACKHOLE_BQ.

- Remove UPD_INPLACE1 and replace it with UPD_IND in the two places it
  was used.  UPD_INPLACE1 wouldn't have worked in a generational setting.