(verify_volume): Call set_next_block_after

(verify_volume): Call set_next_block_after
if read_header returns HEADER_FAILURE
Destroy and reinitialize content of current_stat_info and
extended_header after each iteration.
Issue a warning if the archive created contains some members
whose file names were stripped off their leading prefixes.
This is a temporary fix of the issue reported by Bdale Garbee
<bdale@gag.com> (Refs: Debian bug 230064, Message-Id
<87n07kyzhi.fsf@rover.gag.com>, Sun, 15 Feb 2004 11:22:17 -0700)