r=Andreas Dilger

Description: Addition of EXT3_FEATURE_RO_COMPAT_DIR_NLINKS flag for
             > 32000 subdirectories

Details    : Add EXT3_FEATURE_RO_COMPAT_DIR_NLINK flag to
             EXT3_FEATURE_RO_COMPAT_SUPP. This flag will be set whenever
             subdirectory count crosses 32000. This will aid e2fsck to
             correctly handle more than 32000 subdirectories.