bug#5851: 24.0.50; first character after opening quote often gets eaten in CC modes

[Paul Pogonyshev]

FWIW the bug is still present.  I get this backtrace (2011-02-19
build):

    (error "Invalid search bound (wrong side of point)")
      signal(error ("Invalid search bound (wrong side of point)"))
      byte-code("b\210\302     @       A\"\207" [start err signal] 3)
      c-syntactic-re-search-forward("[;{}]" 8510 end)
      c-before-change-check-<>-operators(6462 6462)
      #[(fn) " \n\"\207" [fn beg end] 3](c-before-change-check-<>-operators)
      mapc(#[(fn) "    \n\"\207" [fn beg end] 3] (c-extend-region-for-CPP 
c-before-change-check-<>-operators))
      c-before-change(6462 6462)
      self-insert-command(1)
      call-interactively(self-insert-command nil nil)

I cannot find a reliable way to reproduce, but it happens often
enough.  Apparently, buffers not touched in quite a while are more
prone.  I.e. open a C++ file and leave it alone for 5 minutes.  Then
switch to the buffer and type outside any string a double quote
following by any other character --- the second character will likely
get eaten with an error as above.  M-x toggle-debug-on-error helps
spotting it.

Paul