add debugfs command to print known features

Print out the currently supported features of e2fsprogs/libext2fs
via a new "debugfs supported_features" command.  This helps scripts
to know whether it is possible to try and enable specific features
in the filesystem.

Signed-off-by: Kalpak Shah <kalpak.shah@sun.com>
Signed-off-by: Andreas Dilger <adilger@sun.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
5 files changed