Activated bli_packm_acquire_mpart_t2b().
Activated bli_packm_acquire_mpart_t2b().

Details:
- Removed the overly-paranoid bli_abort() from the end of
  bli_packm_acquire_mpart_t2b(), to allow others to experiment with
  partitioning through packed blocks of A. Also, and more importantly,
  changed an earlier check that was causing an erroneous (but
  coincidentally redundant) abort(). Also, updated some of the comments
  in bli_packm_part.c.

arm-hpc/blis,xianyi/blis,arm-hpc/blis,scibuilder/blis,audiofilter/blis,rwl/blis,xianyi/blis,rwl/blis,xianyi/blis,arm-hpc/blis,arm-hpc/blis,rwl/blis,audiofilter/blis,xianyi/blis,audiofilter/blis,rwl/blis,scibuilder/blis,scibuilder/blis,scibuilder/blis,audiofilter/blis