zsh 4.3.4: bindkey -s xx 'yyy\n' no longer works (with bindkey -v)

[Jim Meyering <jim@xxxxxxxxxxxx>]

Hello,
First, thanks for maintaining zsh!

I've used the following for ages:

    # Make ^X^X do !!\n
    # This is more direct, but not as nice: bindkey -s '^x^x' '!!\n'
    bangbang () {
      zle .up-history
      zle .accept-line
    }
    zle -N repeat-last-command bangbang
    bindkey '^x^x' repeat-last-command

With 4.2.5, it stopped working.
A little experimenting suggests that no multi-character
LHS sequence works.

With e.g., 4.2.5, the following worked fine:

  g$ zsh -f
  g% bindkey -v
  g% bindkey -s '^x^x' '!!\n'
  g% echo foo
  foo
  g% !!                  <<=== here I typed control-X twice, and no newline
  echo foo               <<=== and it does what I expect
  foo
  g% 

But with 4.3.4, the latter bindkey seems to have no effect:

  r$ zsh -f
  r% bindkey -v
  r% bindkey -s '^x^x' '!!\n'
  r% echo foo
  foo
  r% ^X^X                <<=== here I typed control-X twice,
                               and it merely echos them

I searched the FAQ, release notes, etc. but didn't see any reference to a
deliberate change in behavior.