Code review comment for lp:~jameinel/bzr/2.1-static-tuple-btree-string-intern

This is the same as an earlier patch for using StaticTuple as part of the btree code. It has a couple small additions.

1) Small fix for 'bzr dump-btree' that casts the objects back to tuples for nicer formatting.
2) Add 'StaticTuple' as a type that 'bencode' knows how to deal with (just treats it as another
   Tuple/List object.)
   Arguably we probably want to end up with 'decode_as_tuples=True' to return StaticTuple
   instances. For now, though, this was all that was necessary to get the test suite to pass on my
   machine. (Though a lot of the tests that were failing on PQM weren't failing here anyway...)