(keep-lines-read-args): Add INTERACTIVE arg.

(keep-lines-read-args): Add INTERACTIVE arg.
(keep-lines): Add INTERACTIVE arg.  Never delete lines only
partially contained in the active region.  Do not take active
region into account when called from Lisp, unless INTERACTIVE arg
is non-nil.  Use `forward-line' instead of `beginning-of-line' to
avoid trouble with fields.  Make marker point nowhere when no
longer used.  Always return nil.  Doc fix.
(flush-lines): Add INTERACTIVE arg.  Do not take active region
into account when called from Lisp, unless INTERACTIVE arg is
non-nil.  Use `forward-line' instead of `beginning-of-line' to
avoid trouble with fields.  Make marker point nowhere when no
longer used.  Always return nil.  Doc fix.
(how-many): Add INTERACTIVE arg.  Make RSTART and REND args
interchangeable.  Do not take active region into account when
called from Lisp, unless INTERACTIVE arg is non-nil.  Do not print
message in echo area when called from Lisp, unless INTERACTIVE arg
is non-nil.  Avoid saying "1 occurrences".  Do not use markers.
Return the number of matches.  Doc fix.
(occur): Doc fix.
(perform-replace): Make comment follow double space convention for
the sake of `outline-minor-mode'.