Details:
- Changed the pack_t enumerations so that BLIS_PACKED_VECTOR no longer has
its own value, and instead simply aliases to BLIS_PACKED_UNSPEC. This
makes room in the three pack_t bits of the info field of obj_t so that
two values are now unused, and may be used for other future purposes.
- Updated sloppy terminology usage in comments in level-2 front-ends.
(Replaced "is contiguous" with more accurate "has unit stride".)