_expand_alias does not expand aliases that contain an "!"

[Jonathan H <pythonnut@xxxxxxxxx>]

Hello everyone!

Aliases that contain an exclamation point are not correctly expanded
by _expand_alias. For example:

    [pythonnut ~.z <2>]% zsh -f
    Heptagon% autoload -Uz compinit && compinit
    Heptagon% bindkey "^X^E" _expand_alias
    Heptagon% alias 'gc!'="git commit --amend"
    Heptagon% alias ls="echo"
    Heptagon%

ls will expand on ^X^E to "echo " but gc! won't.

Thanks,
PythonNut