chattr/lsattr: expose FS_NOCOMP_FL (aka EXT2_NOCOMPR_FL)

chattr/lsattr: expose FS_NOCOMP_FL (aka EXT2_NOCOMPR_FL)

This adds support for setting/querying the FS_NOCOMP_FL/EXT2_NOCOMPR_FL
file flag to chattr/lsattr. I picked the character "m" because it was
so far unused and all other characters that were more obvious candidates
were already taken.

The flag is available on btrfs, and with this patch it is possible to
manage it correctly.

Signed-off-by: Lennart Poettering <lennart@poettering.net>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>