Enable FLEX_BG feature support

Enable FLEX_BG feature support

Add FLEX_BG as a supported feature bit.

Add support to mke2fs to create filesystems with FLEX_BG.

Add support to tune2fs to add (and remove, if it won't break
filesystem consistency) the FLEX_BG feature.

Signed-off-by: Jose R. Santos <jrs@us.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
--

 lib/e2p/feature.c   |    2 ++
 lib/ext2fs/ext2fs.h |    6 ++++--
 misc/mke2fs.c       |    7 ++++++-
 3 files changed, 12 insertions(+), 3 deletions(-)