dd improvements.

Support hex (requested by users).

Support status=noxfer and status=none (requested by users).

Fix status output.

Clarify large numbers in --help output.

Use O_TRUNC rather than ftruncate unless we're also seeking.

New tests.

Also partial cleanup (reuse of existing code, removal of non-GLOBALS globals,
and merge dd_main and do_dd).
3 files changed