function returns a comma separated string of the file flags represented by
If no flags are set a zero length string is returned.
If memory cannot be allocated for the return value,
The value returned from
is obtained from
and should be returned to the system with
when the program is done with it.
function takes a string of file flags, as described in
parses it, and returns the set flags and clear flags
such as would be given as arguments to
returns 0, otherwise it returns non-zero and
is left pointing to the offending token.