bug#21957: 24.5; Make occur search within regions when there is one

[b4283@itsuwa.org]

This is a wish request.

The current occur implementation doesn't include a `region' version
which search only within the current region mark by user, instead it
operates on the entire buffer.

It would come in handy if occur searchs within regions as well. Such
behavior is desired, for example, when listing the occurances of a
symbol in the body of a function definition.



In GNU Emacs 24.5.1 (x86_64-unknown-linux-gnu, GTK+ Version 3.16.6)
 of 2015-09-10 on foutrelis
Windowing system distributor `The X.Org Foundation', version 11.0.11704000
System Description:	Arch Linux

Configured using:
 `configure --prefix=/usr --sysconfdir=/etc --libexecdir=/usr/lib
 --localstatedir=/var --with-x-toolkit=gtk3 --with-xft
 'CFLAGS=-march=x86-64 -mtune=generic -O2 -pipe -fstack-protector-strong
 --param=ssp-buffer-size=4' CPPFLAGS=-D_FORTIFY_SOURCE=2
 LDFLAGS=-Wl,-O1,--sort-common,--as-needed,-z,relro'

Important settings:
  value of $LC_CTYPE: zh_TW.UTF-8
  value of $LANG: zh_TW.UTF-8
  value of $XMODIFIERS: @im=gcin
  locale-coding-system: utf-8-unix

Major mode: C++/l

Minor modes in effect:
  shell-dirtrack-mode: t
  nyan-mode: t
  global-linum-mode: t
  linum-mode: t
  ido-everywhere: t
  show-paren-mode: t
  tooltip-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  global-prettify-symbols-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
  column-number-mode: t
  line-number-mode: t
  transient-mark-mode: t
  abbrev-mode: t

Recent messages:

Load-path shadows:

Features:
(shadow sort gnus-util mail-extr emacsbug message idna format-spec
rfc822 mml 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 shell pcomplete grep+ grep compile comint
ansi-color etags ring misearch multi-isearch cc-langs cc-mode-expansions
cc-mode cc-fonts cc-guess cc-menus cc-cmds cc-styles cc-align cc-engine
cc-vars cc-defs smooth-scrolling vc-git quail help-mode jka-compr
expand-region text-mode-expansions er-basic-expansions thingatpt
expand-region-core expand-region-custom nyan-mode buffer-move linum
edmacro kmacro cl-loaddefs cl-lib ido xemacs-theme paren delsel
cus-start cus-load windmove afternoon-theme-autoloads
cherry-blossom-theme-autoloads colorsarenice-theme-autoloads
geiser-autoloads helm-autoloads js2-mode-autoloads info easymenu
php-mode-autoloads rust-mode-autoloads advice help-fns
toml-mode-autoloads package epg-config time-date china-util tooltip
electric uniquify ediff-hook vc-hooks lisp-float-type mwheel x-win x-dnd
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 dynamic-setting system-font-setting
font-render-setting move-toolbar gtk x-toolkit x multi-tty emacs)

Memory information:
((conses 16 727609 127367)
 (symbols 48 27690 0)
 (miscs 40 1313 683)
 (strings 32 121297 25891)
 (string-bytes 1 1561851)
 (vectors 16 91267)
 (vector-slots 8 1181120 133080)
 (floats 8 89 446)
 (intervals 56 7376 3100)
 (buffers 960 23)
 (heap 1024 75181 2588))