when fparseln was first introduced, it put in libutil instead of
libc (for reasons I can't exactly remember; probably to do with
`polluting' libc, but we have weak aliases for a reason...)

anyway, there have been times in various libc functions where it
would be useful to be able to call fparseln, and that's no good
if fparseln is in libutil.

i propose that we move fparseln from libutil into libc.

what's exactly required to do this? didn't we have problems moving
pw_scan() from libutil to libc in the past, so libc compiles in a
private version of pw_scan as __pw_scan, which strikes me as being
a bit of a hack...

thoughts?