Font-lock '...' strings, plus various simplifications and fixes.

Font-lock '...' strings, plus various simplifications and fixes.
* lisp/progmodes/octave-mod.el (octave-font-lock-keywords): Use regexp-opt.
(octave-font-lock-close-quotes): New function.
(octave-font-lock-syntactic-keywords): New var.
(octave-mode): Use it.  Set beginning-of-defun-function.
(octave-mode-map): Don't override the <foo>-defun commands.
(octave-mode-menu): Pass it directly to easy-menu-define;
remove (now generic) <foo>-defun commands; use info-lookup-symbol.
(octave-block-match-alist): Fix up last change so that
octave-close-block uses the more specific keyword.
(info-lookup-mode): Silence byte-compiler.
(octave-beginning-of-defun): Not interactive any more.
Optimize slightly.
(octave-end-of-defun, octave-mark-defun, octave-in-defun-p): Remove.
(octave-indent-defun, octave-send-defun): Use mark-defun instead.
(octave-completion-at-point-function): Make sure point is within
beg..end.
(octave-reindent-then-newline-and-indent):
Use reindent-then-newline-and-indent.
(octave-add-octave-menu): Remove.