Details:
- These changes were intended for the previous commit.
- Defined bli_gemm_determine_kc_[fb]() and bli_gemm_determine_kc_[fb](),
which determine blocksizes for gemm-based operations, taking special
care to "nudge" the kc dimension up to a multiple of MR or NR for
hemm and symm operations, as needed.
- Changed bli_gemm_blk_var3f.c to call bli_gemm_determine_kc_f().
instead of bli_determine_blocksize_f().
- Comment updates to bli_trmm_blocksize.c, bli_trsm_blocksize.c.