(<quotearg.h>): New include.

(<quotearg.h>): New include.
(start_header): Use `member names' to refer to archive member names, not
`archive names'.  Warn about `..' in member names.
(finish_sparse_file, dump_file):
Quote arbitrary strings in diagnostics.
(finish_sparse_file, dump_file):
Don't assume that gettext preserves errno.
(dump_file): Don't use `access' to determine whether a directory is readable;
this isn't reliable if tar is setuid.  Use `opendir' instead.
Check for readdir and closedir failures.
Don't dump sockets as if they were fifos; just warn and skip.