filefrag: minor usability improvements

filefrag: minor usability improvements

Add '-V' to filefrag to print the installed version of the tool.

If '-V' is used twice, print out the list of supported FIEMAP flags.
This can be used to check if filefrag understands a specific feature.

Include FIEMAP in the error message printed when filefrag cannot
get the file layout. Since FIEMAP is commonly available and tried
first, it should also be mentioned in the error message unless it
was requested to only run FIBMAP.

Update filefrag.1.in man page to cover the new -V option.

Fix a formatting error with the recently added '-P' options, and
include '-E' and '-P' in the SYNOPSIS section.

Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Lustre-bug-id: https://jira.whamcloud.com/browse/LU-11848
Reviewed-by: Wang Shilong <wshilong@whamcloud.com>
Change-Id: Ib126bdd70efa1775aef6db761f54e27a593ebbe5
Signed-off-by: Theodore Ts'o <tytso@mit.edu>