mkfs: default to CRC enabled filesystems

mkfs: default to CRC enabled filesystems

It's time to change the mkfs defaults to enable CRCs for all new
filesystems. While there, also enable the free inode btree by
default, too, as that functionality has also had long enough to make
it into distro kernels, too. Also update the man page to reflect the
change in defaults.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>