Ropebwt3-3.4 (r167)

Notable changes:

• Improvement: in sw, removed out-of-band cells earlier. This speeds up
  BWA-SW by 20%.

• Improvement: sw now computes positions in each thread. This improves the
  multi-threading performance for short queries.

• Bugfix: with mem, ambiguous bases in query caused segmentation fault.
  Ropebwt3 now converts ambiguous bases to "A". This does not affect sw.

• Breaking: removed greedy MEM

(3.4: 20 August 2024, r167)