Compsys fails badly with "setopt ignorebraces"

[Bart Schaefer <schaefer@brasslantern.com>]

zsh% ls {<TAB>

Long stream of error messages (depends on values in completer style); if I
remove the repeated errors, I'm left with:

_arguments:comparguments:208: invalid argument: (--all -a -A --almost-all){--all,-a}[list entries starting with .]

(That one must really come from "_ls", not _arguments itself.  I suspect a
lot of completion functions use braces to shortcut _arguments lists.)

_match:72: parse error near `then'

_approximate:89: parse error near `then'

(Those two seem to be real bugs, at least in the documentation -- an
undocumented side-effect of ignorebraces is that "{ command }" is not
valid syntax any more: rather you need the semicolon "{ command ; }"
as in bash/ksh.)

BUG: old_heaps() with pushed heaps

(No idea.)

We could (probably should) add NO_ignorebraces to _comp_options, but the
_expand completer does modify its behavior based on that option, so it
would be nice to propagate the original value somehow.