write_idx: make filename char* non-const (fixes python 2.6.6 compatibility).

Thanks to Alexander Barton <alex@barton.de> for the report.

Signed-off-by: Rob Browning <rlb@defaultvalue.org>
Quash stat(2) st_rdev unless we're going to need it for mknod().

On some platforms (i.e. kFreeBSD), the st_rdev value isn't completely
stable.  For example, given "date > foo; cp -a foo foo-2", the st_rdev
value may differ between the two files.

Since we only need the st_rdev value for the call to mknod() when
restoring character and block special files, set it to zero for
anything else.

Signed-off-by: Rob Browning <rlb@defaultvalue.org>
Ignore unimplemented metadata record during read (_rec_tag_nfsv4_acl).

Don't test for _rec_tag_nfsv4_acl and then try to call an
unimplemented method in Metadata.read().  Otherwise, if/when we do add
support, older versions of bup will choke on it.

Thanks to Alexander Barton <alex@barton.de> for pointing this out.

Signed-off-by: Rob Browning <rlb@defaultvalue.org>