Reimplemented unit blocksize fix in prev commit.

Details:
- Instead of inferring the storage format of the micro-panels from within
  the packm variants, we now pass in a bool_t value that denotes whether
  the packed matrix contains row-stored column panels or column-stored
  row panels. This value can then be tested more easily inside the main
  packm variant loop.
- Renumbered pack_t schema values in bli_type_defs.h so that there are
  now five bits, each with different meaning:
  - 4: packed or not packed?
  - 3: packed for 3m?
  - 2: packed for 4m?
  - 1: packed to panels?
  - 0: stored by rows or columns?
- Added new macros that test for status of above bits in schema bit
  subfield, and renamed some existing macros related to 4m/3m.
Redefined bit field macros with bitshift operator.

Details:
- Redefined many of the macros that define bit fields and bit values in
  the obj_t info field using the bitshift operator (<<). This makes it
  easier to reorder bit fields, or expand existing bit fields, or add
  new fields. The bitshifting should be evaluated by the compiler at
  compile-time.