Log Message:
Mirror change in archivers/mtree by <heinz> on 2004/04/16:

Introduce HAVE_FILE_FLAGS if the system declares UF_SETTABLE and SF_SETTABLE
in addition to member 'st_flags' of struct stat. Use HAVE_FILE_FLAGS instead
of HAVE_STRUCT_STAT_ST_FLAGS.
This avoids confusion on UnixWare which has 'st_flags' but does _not_ support
file flags.