console: add 'show cache' for debugging
blk: possibly fix entry reuse
all: replace error returns with constants.
tree: refcount blocks correctly
cons: improve output
bptr: move to 24 byte block pointers with generations
refactor: move to Bptr struct
scan: fix tree boundary condition
fscons: tweak 'show' to take args
fs: handle truncation a bit better, accumulate messages correctly
scan: don't drop files in directory listing
tree: refactor to allow multiple parallel trees
blk: fix freelist implementaton
fs: allocate blocks correctly, group insertions, snapshot
tree: shrink buffer when flushing deletions.