bug#20641: 24.5; add-file-local-variable should special-case lexical-binding

[Philipp Stephani]

Given that `lexical-binding' only works when set in the first line of
the file, `add-file-local-variable' should defer to
'add-file-local-variable-prop-line' for this variable only.



In GNU Emacs 24.5.1 (x86_64-apple-darwin14.1.0, NS apple-appkit-1344.72)
 of 2015-04-12 on p
Configured using:
 `configure --prefix=/usr/local/Cellar/emacs/24.5
 --enable-locallisppath=/usr/local/share/emacs/site-lisp
 --infodir=/usr/local/Cellar/emacs/24.5/share/info/emacs
 --with-file-notification=gfile --with-dbus --with-gnutls --with-rsvg
 --with-imagemagick --without-popmail --with-ns
 --disable-ns-self-contained'

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

Major mode: Emacs-Lisp

Minor modes in effect:
  tooltip-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent messages:
Mark set
Setting `send-mail-function' temporarily since "emacs -q" would overwrite 
customizations
Sending...
Mark set [2 times]
Sending via mail...
Setting `smtpmail-smtp-server' temporarily since "emacs -q" would overwrite 
customizations
Setting `smtpmail-smtp-service' temporarily since "emacs -q" would overwrite 
customizations
Sending email 
Sending email done
Sending...done

Load-path shadows:
None found.

Features:
(gnutls network-stream starttls tls mailalias smtpmail auth-source eieio
byte-opt bytecomp byte-compile cl-extra cconv eieio-core password-cache
cus-edit cus-start cus-load wid-edit cl-loaddefs cl-lib help-mode pp
shadow sort gnus-util mail-extr emacsbug message format-spec rfc822 mml
easymenu mml-sec mm-decode mm-bodies mm-encode mail-parse rfc2231
mailabbrev gmm-utils mailheader sendmail rfc2047 rfc2045 ietf-drums
mm-util mail-prsvr mail-utils warnings help-fns files-x xterm time-date
tooltip electric uniquify ediff-hook vc-hooks lisp-float-type mwheel
ns-win tool-bar dnd fontset image regexp-opt fringe tabulated-list
newcomment lisp-mode prog-mode register page menu-bar rfn-eshadow timer
select scroll-bar mouse jit-lock font-lock syntax facemenu font-core
frame cham georgian utf-8-lang misc-lang vietnamese tibetan thai
tai-viet lao korean japanese hebrew greek romanian slovak czech european
ethiopic indian cyrillic chinese case-table epa-hook jka-cmpr-hook help
simple abbrev minibuffer nadvice loaddefs button faces cus-face macroexp
files text-properties overlay sha1 md5 base64 format env code-pages mule
custom widget hashtable-print-readable backquote make-network-process
dbusbind gfilenotify cocoa ns multi-tty emacs)

Memory information:
((conses 16 111890 8826)
 (symbols 48 20879 0)
 (miscs 40 51 185)
 (strings 32 18684 5217)
 (string-bytes 1 517213)
 (vectors 16 10719)
 (vector-slots 8 371236 4716)
 (floats 8 77 318)
 (intervals 56 423 24)
 (buffers 960 18))