busybox

* archival/bunzip2.c: Include <unistd.h>.
  (bunzip2_main): Read data from standard input if FILE argument is `-' or
  omitted.
* include/usage.h (bunzip2_trivial_usage, bunzip2_full_usage): Rewrite.
* testsuite/bunzip2/bunzip2-reads-from-standard-input: New.