e2fsck: fix entries with invalid encoded characters

e2fsck: fix entries with invalid encoded characters

On strict mode, invalid Unicode sequences are not permited.  This patch
adds a verification step to pass2 to detect and modify the entries with
the same replacement char used for non-encoding directories '.'.

After the encoding test, we still want to check the name for usual
problems, '\0', '/' in the middle of the sequence.

Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
Signed-off-by: Arnaud Ferraris <arnaud.ferraris@collabora.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>