that until all current uses of IFS are complete (as we have IFS's
value cached in ifs - if IFS alters, ifs might point anywhere).
Handle this by deferring assignments to IFS until everything is done.
This makes us appear to comply with the (currently) proposed requirement
for read by POSIX that field splitting complete before vars are
assigned. (Other shells, like dash, ksh93, yash, bosh behave like this)
That might end up being unspecified though, as other shells (bosh,
mksh) assign each field to its var as it is delimited (though bosh
appears to have bugs). If we wanted to go that route, the issue here
could have been handled by re-doing the init of ifs after every
setvar() that is performed here (except the last, after which it is
no longer needed).
XXX pullup -10
28b2f4e3f6