Merge .netrc's token() file-reading loops; quoted and not.

Merge .netrc's token() file-reading loops;  quoted and not.

Check for ferror(3) as well as feof(3) on entry.
Comment on lack of definition of quoted-string syntax, e.g. «"foo""bar"»
is two tokens without needing a separator.
Add comments on bugs for first non-quote character of a token being
backslash, and if a backslash escapes EOF.