e2fsck: print thread log properly

e2fsck: print thread log properly

When multi-thread fsck is enabled, logs printed from multiple
threads could overlap with each other. The overlap sometimes
makes the logs unreadable because log_out() is used multiple times
for a single line.

This patch adds leading [Thread XXX] to each logs if multi-thread
is enabed by -m option.

This patch also adds message to show the group ranges and inode
numbers for each thread, which is useful for debuging multi-thread
check.

E2fsprogs-commit: 5b071ed80deca2cdc87585a673076529dd47ca6e

Change-Id: I4bd08bc48813a399ab3a79130ff159b12d22f3a0
Signed-off-by: Li Xi <lixi@ddn.com>
Signed-off-by: Wang Shilong <wshilong@ddn.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>