Unsquashfs: add comment regarding SQUASHFS_TRACE and the progress bar

Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk>
Mksquashfs: flags should be set using TRUE/FALSE and not 0/1

Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk>
Mksquashfs: move progress bar disable

Originally when file writing had finished in dir_scan() the
progress bar was disabled.  However, at this point there can
be queued fragments still to be compressed, and blocks queued
still to be written.

On a fast system and fast output device, this doesn't matter, as
the gap between the progress bar stopping and mksquashfs finishing
is small, as any fragments and blocks are quickly dealt with.

However, on a slow system or a slow output device, large queues
of fragments and/or blocks can have built up, which may time a while
to compress and/or write.  Having the progress bar stop before
this is done can be confusing, as it looks like Mksquashfs has hung.

So move progress bar disabling to after fragment compression and
block writing has finished.

Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk>
squashfs-tools - xattr.h:127:22: error: parameter name omitted

      Hello maintainer of squashfs-tools,

In Gentoo bug report 498798[1], we came across a slight problem when
XATTR_SUPPORT is disabled:

In file included from read_fs.c:50:0:
xattr.h: In function ‘get_xattr’:
xattr.h:127:22: error: parameter name omitted
 static inline struct xattr_list *get_xattr(int i, unsigned int *count,
int)
                      ^
<builtin>: recipe for target 'read_fs.o' failed
make: *** [read_fs.o] Error 1

The attached patch fixes the problem for whoever wants to use
[mk|un]squashfs without support for extended attributes.

Regards,
     jer

[1] https://bugs.gentoo.org/show_bug.cgi?id=498798