bug#4192: 23.1; special fontification for "//" in cc-mode

[Tom Tromey <tromey@redhat.com>]

Please write in English if possible, because the Emacs maintainers
usually do not have translators to read other languages for them.

Your bug report will be posted to the bug-gnu-emacs@gnu.org mailing list,
and to the gnu.emacs.bug news group.

Please describe exactly what actions triggered the bug
and the precise symptoms of the bug:


This is a feature request for cc-mode.

I work on a number of projects that use C89, not C99.  In these
projects, it is invalid to use "//"-style comment.  It would be nice if
cc-mode would optionally flag such comments in a special face, so that I
can immediately see when I've written a comment incorrectly.


If Emacs crashed, and you have the Emacs process in the gdb debugger,
please include the output from the following gdb commands:
    `bt full' and `xbacktrace'.
If you would like to further debug the crash, please read the file
/usr/share/emacs/23.1/etc/DEBUG for instructions.


In GNU Emacs 23.1.1 (i386-redhat-linux-gnu, GTK+ Version 2.16.5)
 of 2009-08-03 on x86-5.fedora.phx.redhat.com
Windowing system distributor `The X.Org Foundation', version 11.0.10601901
configured using `configure  '--build=i386-redhat-linux-gnu' '--host=i386-redhat-linux-gnu' '--target=i586-redhat-linux-gnu' '--program-prefix=' '--prefix=/usr' '--exec-prefix=/usr' '--bindir=/usr/bin' '--sbindir=/usr/sbin' '--sysconfdir=/etc' '--datadir=/usr/share' '--includedir=/usr/include' '--libdir=/usr/lib' '--libexecdir=/usr/libexec' '--localstatedir=/var' '--sharedstatedir=/var/lib' '--mandir=/usr/share/man' '--infodir=/usr/share/info' '--with-dbus' '--with-gif' '--with-jpeg' '--with-png' '--with-rsvg' '--with-tiff' '--with-xft' '--with-xpm' '--with-x-toolkit=gtk' 'build_alias=i386-redhat-linux-gnu' 'host_alias=i386-redhat-linux-gnu' 'target_alias=i586-redhat-linux-gnu' 'CFLAGS=-DMAIL_USE_LOCKF -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-bu
 ffer-size=4 -m32 -march=i586 -mtune=generic -fasynchronous-unwind-tables''

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: nil
  locale-coding-system: utf-8-unix
  default-enable-multibyte-characters: t

Major mode: Fundamental

Minor modes in effect:
  erc-list-mode: t
  erc-menu-mode: t
  erc-autojoin-mode: t
  erc-ring-mode: t
  erc-pcomplete-mode: t
  erc-track-mode: t
  erc-track-minor-mode: t
  erc-match-mode: t
  erc-button-mode: t
  erc-fill-mode: t
  erc-stamp-mode: t
  erc-netsplit-mode: t
  erc-spelling-mode: t
  erc-truncate-mode: t
  diff-auto-refine-mode: t
  shell-dirtrack-mode: t
  highlight-changes-visible-mode: t
  erc-status-mode: t
  erc-services-mode: t
  erc-networks-mode: t
  erc-irccontrols-mode: t
  erc-noncommands-mode: t
  erc-move-to-prompt-mode: t
  erc-readonly-mode: t
  tooltip-mode: t
  mouse-wheel-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  global-auto-composition-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent input:
e a t u r e s , SPC b u t SPC i t SPC d i d SPC b r 
e a k SPC w 3 m - e l SPC f o r SPC m e SPC : ( <return> 
n o SPC m o r e SPC h t m l SPC m a i l SPC f o r SPC 
a SPC w h i l e <return> <switch-frame> <switch-frame> 
m a y b e SPC t h a t SPC i s SPC a SPC p l u s SPC 
<return> <f10> <f10> <f10> M-v M-> <f10> C-z o C-x 
b P <return> C-x k <return> C-x b L <tab> <return> 
C-v C-v M-v M-v M-v C-z o <f10> <f10> <f10> <f10> C-h 
i d m c c <tab> SPC m <tab> <return> C-v C-l m o d 
<tab> <return> l C-v C-s c o m m e n t C-a m <return> 
C-v C-s C-s C-v M-> C-s C-s C-s C-s C-s C-s C-s C-a 
C-v M-> C-s C-s C-s C-s C-a n n n n C-s C-s C-a SPC 
n u n n p 1 u SPC SPC SPC SPC SPC SPC p SPC n SPC n 
n u n SPC SPC SPC SPC SPC SPC SPC SPC SPC SPC SPC SPC 
<backspace> n SPC SPC SPC SPC SPC SPC SPC SPC SPC SPC 
SPC n SPC SPC SPC SPC SPC SPC n n n n n n C-s / / C-a 
C-v n C-s C-s C-a n n t C-s / / C-s C-s C-s C-s C-s 
C-s C-s C-s C-s C-s C-s C-s C-s C-s C-s C-s C-s C-a 
q C-z o M-x r e p r o t - e C-u C-b C-b C-f C-t C-e 
m <tab> <return>

Recent messages:
call-interactively: End of buffer
Mark set
Mark saved where search started
Mark set
Mark saved where search started
Info-extract-pointer: Node has no Next [2 times]
Searching subfile ccmode-2...
uncompressing ccmode-2.gz...done
uncompressing ccmode-1.gz...done
Mark saved where search started

Tom