changes for whiteouts and union filesystem

4.4BSD snapshot (revision 8.1); add 1993 to copyright

rename file flags to UF_* and SF_*, minimize name space problems

two new routines for file flags: flags_to_string and string_to_flags
currently used by chflags(1) and install(1)
date and time created 93/03/03 20:37:50 by bostic