faster VECTOR-SUBSEQ*

faster VECTOR-SUBSEQ*

  Use a WITH-ARRAY-DATA to get to the underlying vector, and use a widetag
  dispatch table to pick the correct SUBSEQ implementation for the underlying
  type.

  This is actually just as fast even for simple strings as STRING-SUBSEQ*, so
  throw it out.

  Also make inlining SUBSEQ conditional on SPEED > SPACE now that the
  out-of-line version doesn't suck so much.

  Fixes lp#902537.