bug#28916: 25.1; octave-block-offset should be safe as file-local variable

[Benjamin Moody]

The variable 'octave-block-offset' determines the number of spaces used
for automatically indenting Octave code.

Like similar variables used in other modes (e.g. c-basic-offset), it is
often desirable to set this variable on a per-file or per-directory
basis, in order to conform with a project's existing indentation style.

Thus, this variable should be marked as "safe as a file local variable
if its value satisfies the predicate ‘integerp’."

The same would seem to apply to 'octave-continuation-offset', but that
variable doesn't appear to actually be used (continuation lines are
indented based on the syntactic context.)

--
In GNU Emacs 25.1.1 (x86_64-pc-linux-gnu, GTK+ Version 3.22.11)
 of 2017-09-15, modified by Debian built on trouble
Windowing system distributor 'The X.Org Foundation', version 11.0.11902000
System Description:     Debian GNU/Linux 9.1 (stretch)

Configured using:
 'configure --build x86_64-linux-gnu --prefix=/usr
 --sharedstatedir=/var/lib --libexecdir=/usr/lib
 --localstatedir=/var/lib --infodir=/usr/share/info
 --mandir=/usr/share/man --with-pop=yes
 
--enable-locallisppath=/etc/emacs25:/etc/emacs:/usr/local/share/emacs/25.1/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/25.1/site-lisp:/usr/share/emacs/site-lisp
 --with-sound=alsa --build x86_64-linux-gnu --prefix=/usr
 --sharedstatedir=/var/lib --libexecdir=/usr/lib
 --localstatedir=/var/lib --infodir=/usr/share/info
 --mandir=/usr/share/man --with-pop=yes
 
--enable-locallisppath=/etc/emacs25:/etc/emacs:/usr/local/share/emacs/25.1/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/25.1/site-lisp:/usr/share/emacs/site-lisp
 --with-sound=alsa --with-x=yes --with-x-toolkit=gtk3
 --with-toolkit-scroll-bars 'CFLAGS=-g -O2
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-fstack-protector-strong
 -Wformat -Werror=format-security -Wall' 'CPPFLAGS=-Wdate-time
 -D_FORTIFY_SOURCE=2' LDFLAGS=-Wl,-z,relro'

Configured features:
XPM JPEG TIFF GIF PNG RSVG IMAGEMAGICK SOUND GPM DBUS GCONF GSETTINGS
NOTIFY ACL LIBSELINUX GNUTLS LIBXML2 FREETYPE M17N_FLT LIBOTF XFT ZLIB
TOOLKIT_SCROLL_BARS GTK3 X11

Important settings:
  value of $LC_COLLATE: C
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix

Major mode: Emacs-Lisp

Minor modes in effect:
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  auto-composition-mode: t
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Recent messages:
Loading /etc/emacs/site-start.d/50w3m-el.el (source)...done
Loading /etc/emacs/site-start.d/51debian-el.el (source)...done
Loading gnus...done
For information about GNU Emacs and the GNU system, type C-h C-a.
Package iswitchb is obsolete!
Please type y, n, or !: y
Making completion list...
Type C-x 1 to delete the help window.
uncompressing octave.el.gz...done
Note: file is write protected

Load-path shadows:
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/usr/share/emacs/site-lisp/debian-startup
/usr/share/emacs25/site-lisp/flim/hex-util hides 
/usr/share/emacs/25.1/lisp/hex-util
/usr/share/emacs25/site-lisp/flim/md4 hides /usr/share/emacs/25.1/lisp/md4
/usr/share/emacs/site-lisp/rst hides /usr/share/emacs/25.1/lisp/textmodes/rst
/home/benjamin/elisp/js hides /usr/share/emacs/25.1/lisp/progmodes/js
/usr/share/emacs25/site-lisp/flim/hmac-md5 hides 
/usr/share/emacs/25.1/lisp/net/hmac-md5
/usr/share/emacs25/site-lisp/flim/sasl-digest hides 
/usr/share/emacs/25.1/lisp/net/sasl-digest
/usr/share/emacs25/site-lisp/flim/ntlm hides /usr/share/emacs/25.1/lisp/net/ntlm
/usr/share/emacs25/site-lisp/flim/sasl-ntlm hides 
/usr/share/emacs/25.1/lisp/net/sasl-ntlm
/usr/share/emacs25/site-lisp/flim/sasl-cram hides 
/usr/share/emacs/25.1/lisp/net/sasl-cram
/usr/share/emacs25/site-lisp/flim/hmac-def hides 
/usr/share/emacs/25.1/lisp/net/hmac-def
/usr/share/emacs25/site-lisp/flim/sasl hides /usr/share/emacs/25.1/lisp/net/sasl

Features:
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Memory information:
((conses 16 120847 7652)
 (symbols 48 23557 0)
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 (strings 32 23757 5135)
 (string-bytes 1 673281)
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