- added buck2obj_flush() that flushed the memory pool (some caller only

- added buck2obj_flush() that flushed the memory pool (some caller only
  remember struct buck2obj_buf * and since it is not exported, they could not
  flush it by themselves)
- obj_read_bucket() returns the length of the header if requested
- adapted to growing buffers (gbuf.h)
- updated interface of bconfig()
- lizard_decompress_safe() automatically realloc's the buffer, hence the
  wrapper is not needed