reiser4: rewrite handling compressed files at flush time

This is mostly equivalent transform.
The result looks better, there are more chances to understand what is
going on.

Signed-off-by: Edward Shishkin <edward.shishkin@gmail.com>
reiser4: don't panic in do_readpage_ctail

Don't panic when unprepped ctail cluster is found.
Instead, return error and suggest to fsck.

Signed-off-by: Edward Shishkin <edward.shishkin@gmail.com>
reiser4: fix up compile errors when debug is on

Signed-off-by: Edward Shishkin <edward.shishkin@gmail.com>